Seeing Well Underwater (If You Dive, Please read!)
Gurzeler
myself!
Back in the days when I wore glasses, I would go diving from time to time
and discovered that I did not need to wear my glasses underwater. This,
of course, was wonderful because I didn't need to even think about
prescription goggles (I'll bet they're expensive!). The minute I got out
of the water, of course, I was back to being blind :-)
Why is this? Is it because water refracts and reflects light so many
different ways that one of those rays is bound to enter my poor myopic
eyes and hit the retina just right? Why then, can't I look through a
fishtank and clearly see what's on the other side?
If I am correct about the refractive power of water, does it follow that
people with dry eyes often have more vision problems than people with
nice, moist eyes?
Fred
Nick Jones
Your're sorta on the right track Fred. Its to do with the difference
between the refractive index of air and water. Off the top of my head
water has a refractive index of about 1.3 and air 1.0. The amount
light is refracted (bent)is determined by the change in refractive
index.
There is a large
change when light enters the eye from air as the cornea has a refractive
index of about 1.4. Therefore the light is refracted a large amount.
However, in water there is only a difference in refractive index of about
0.1, so the light is bent significantly less.
It would appear that you are hypermetropic (far sighted) and that
normally light focusses in front of your retina, however as the light
is refracted significantly less in water, the light focusses closer to,
or directly on your retina, thus resulting in clearer vision.
Nick the Orthoptist
William Stacy
>
>gurz...@aol.com (Gurzeler) wrote:
Why then, can't I look through a
>> fishtank and clearly see what's on the other side?
>>
>> If I am correct about the refractive power of water, does it follow that
>> people with dry eyes often have more vision problems than people with
>> nice, moist eyes?
>>
>> Fred
>
>Your're sorta on the right track Fred. Its to do with the difference
>between the refractive index of air and water. Off the top of my head
>water has a refractive index of about 1.3 and air 1.0. The amount
>light is refracted (bent)is determined by the change in refractive
>index.
>There is a large
>change when light enters the eye from air as the cornea has a refractive
>index of about 1.4. Therefore the light is refracted a large amount.
>However, in water there is only a difference in refractive index of
about
>0.1, so the light is bent significantly less.
>
>It would appear that you are hypermetropic (far sighted) and that
>normally light focusses in front of your retina, however as the light
>is refracted significantly less in water, the light focusses closer
to,
>or directly on your retina, thus resulting in clearer vision.
Good answer, Nick.
I'll add the reason it doesn't work for a fish tank is that his cornea
is in contact with air, not water. Now if he'd put his head into the
fish tank, re-establishing the water/cornea interface, he'd be fine.
Incidentally, that would also help his dry eye problem, at least
temporarily.
Bill
The Littl Shynin Man
>
> It would appear that you are hypermetropic (far sighted) and that
> normally light focusses in front of your retina, however as the light
> is refracted significantly less in water, the light focusses closer to,
> or directly on your retina, thus resulting in clearer vision.
>
> Nick the Orthoptist
Nick, isn't it the case that the crucial factor here is the fact that
Water has a *higher* index of refraction than air, and that water in
direct contact with the surface of the cornea becomes in effect a
concave (minus power) lens of moderate power? And that the core defect
in vision is myopia rather than hyperopia?
Of course, if you're wearing a diving mask, all that changes...
Mike
Ken A. Nishimura
: In <4r01vv$b...@perki0.connect.com.au> Nick Jones <njo...@seranis.com.au> writes:
: >Your're sorta on the right track Fred. Its to do with the difference
: >between the refractive index of air and water. Off the top of my head
: >water has a refractive index of about 1.3 and air 1.0. The amount
: >light is refracted (bent)is determined by the change in refractive
: >index.
: >There is a large
: >change when light enters the eye from air as the cornea has a refractive
: >index of about 1.4. Therefore the light is refracted a large amount.
: >However, in water there is only a difference in refractive index of
: about
: >0.1, so the light is bent significantly less.
: >It would appear that you are hypermetropic (far sighted) and that
: >normally light focusses in front of your retina, however as the light
?????????????????????????
: >is refracted significantly less in water, the light focusses closer
: to,
: >or directly on your retina, thus resulting in clearer vision.
: Good answer, Nick.
: I'll add the reason it doesn't work for a fish tank is that his cornea
: is in contact with air, not water. Now if he'd put his head into the
: fish tank, re-establishing the water/cornea interface, he'd be fine.
: Incidentally, that would also help his dry eye problem, at least
: temporarily.
: Bill
I think we have a Optics 101 problem. If the image is focussed
in *front* of the retina, isn't this myopia? Hypermetropic eyes
are optically too short, and the image focuses behind the retina.
Now, the efficacy of a lens is a function of the curvature and
the delta of the indices of refraction at the surfaces. So,
Nick is right -- the delta of the eye in air is about 0.4 while
in water it is about 0.1. Now, the cornea forms a "plus" lens,
so in water, it is less effective as a plus lens in water, or
equivalent to putting a "minus" lens on the surface of the
cornea -- something a myopic person does when s/he puts a
contact lens on.
I think the diver in question is quite myopic. Given that the cornea
represents about 42D of power, one can do a quick calculation
as to his "on-land" ametropia... I guess you'll need K numbers
too.
I agree with the fish tank answer. This is also the reason
why emmetropic people can't see under water, but goggles work.
==ken
Richard Hemenger
>
> If this post seems rather humorous, that's okay; I find it rather amusing
> myself!
>
> Back in the days when I wore glasses, I would go diving from time to time
> and discovered that I did not need to wear my glasses underwater. This,
> of course, was wonderful because I didn't need to even think about
> prescription goggles (I'll bet they're expensive!). The minute I got out
> of the water, of course, I was back to being blind :-)
>
> Why is this? Is it because water refracts and reflects light so many
> different ways that one of those rays is bound to enter my poor myopic
> fishtank and clearly see what's on the other side?
>
Fred, you didn't say whether or not you were using goggles or how
much myopia you had. In an earlier response to your posting it was
correctly pointed out that water in direct contact with your cornea
would nearly cancel out its refractive power thus reducing the power
of the eye by 40+ diopters. It seems unlikely that you could see
well under these circumstances even with high myopia. Let me point
out that even if you wore goggles with plane lenses there is
something for a myope to gain below water as compared to above.
This is simply due to the well-known fore-shortening of all
distances below water by a factor of 4/3 (refractive index of
water). This in effect extends a myope's range of clear vision by
this same factor. To take a definite example a 2.5 diopter myope has
clear vision out to about 16 in. Under water this would be extended
to about 21 in. This is certainly not a huge amount but might give
an impression of improved vision when examining one's immediate
surroundings. When looking through a tank of water your range of
clear vision would also be extended but by a small additive amount
proportional to the thickness of the tank.
Regards
Richard
William Stacy
Nishimura) writes:
>
>William Stacy (w...@ix.netcom.com) wrote:
>: I'll add the reason it doesn't work for a fish tank is that his cornea
>: is in contact with air, not water. Now if he'd put his head into the
>: fish tank, re-establishing the water/cornea interface, he'd be fine.
>
>: Incidentally, that would also help his dry eye problem, at least
>: temporarily.
>
>: Bill
>
>I think we have a Optics 101 problem. If the image is focussed
>in *front* of the retina, isn't this myopia? Hypermetropic eyes
>are optically too short, and the image focuses behind the retina.
>
Absolutely right. My 101 prof would be horrified at my ignoring that!
>Now, the efficacy of a lens is a function of the curvature and
>the delta of the indices of refraction at the surfaces. So,
>Nick is right -- the delta of the eye in air is about 0.4 while
>in water it is about 0.1. Now, the cornea forms a "plus" lens,
>so in water, it is less effective as a plus lens in water, or
>equivalent to putting a "minus" lens on the surface of the
>cornea -- something a myopic person does when s/he puts a
>contact lens on.
>
Very good, Toto.
>I think the diver in question is quite myopic. Given that the cornea
>represents about 42D of power, one can do a quick calculation
>as to his "on-land" ametropia... I guess you'll need K numbers
>too.
>
>I agree with the fish tank answer. This is also the reason
>why emmetropic people can't see under water, but goggles work.
>
> ==ken
Glad to hear they're still teaching optics. Carry on!
Bill
Raymond A. Chamberlin
>If this post seems rather humorous, that's okay; I find it rather amusing
>myself!
>Back in the days when I wore glasses, I would go diving from time to time
>and discovered that I did not need to wear my glasses underwater. This,
>of course, was wonderful because I didn't need to even think about
>prescription goggles (I'll bet they're expensive!). The minute I got out
>of the water, of course, I was back to being blind :-)
>Why is this? Is it because water refracts and reflects light so many
>different ways that one of those rays is bound to enter my poor myopic
>eyes and hit the retina just right? Why then, can't I look through a
>fishtank and clearly see what's on the other side?
Lay comment: The optic index of water is closer to that of your eyes'
optics than that of air, and thus the aberrations in your eyes' optics
do not show up as much. More specifically, I suspect you wear glasses
for myopia, and the higher index of the water results in a longer
focal length from your eyes' optics, so that you see to a further
distance. Of course, in the case of the fish tank, there is air
between your eyes and the tank. For the effect, the water has to be
essentially in contact with your eyes.
>If I am correct about the refractive power of water, does it follow that
>people with dry eyes often have more vision problems than people with
>nice, moist eyes?
I don't think any dry-eyes problem has anything to do with refractive
power, but let the optometrists speak on this.
Ray
Raymond A. Chamberlin
>
.......................
>
>I'll add the reason it doesn't work for a fish tank is that his cornea
>is in contact with air, not water. Now if he'd put his head into the
>fish tank, re-establishing the water/cornea interface, he'd be fine.
Well, if his wife came into the room at the time, she might wonder
just how fine he was.
Ray
Raymond A. Chamberlin
>In <4r14u3$o...@agate.berkeley.edu> ken...@kabuki.EECS.Berkeley.EDU (Ken A.
>Nishimura) writes:
>>
>>
.........................
>>
>>I think we have a Optics 101 problem. If the image is focussed
>>in *front* of the retina, isn't this myopia? Hypermetropic eyes
>>are optically too short, and the image focuses behind the retina.
>>
>Absolutely right. My 101 prof would be horrified at my ignoring that!
Tell me you were recovering from a black widow or courgar bite. Or
were you testing weed to see if it might be good for glaucoma? Guess
you blew your chances of getting back on the Optometry Board. Check
out *my* post on this subject. I haven't checked the date-and-time
stamp on my post relative to Dr. Nishimura's, but I didn't copy any
other "students'" papers around here. And I thought I knew which to
copy--if I ever needed to. . . . I dunno. :-(
>Glad to hear they're still teaching optics. Carry on!
No doubt he sneaked over to Engineering to make sure the prof knew
what he was talking about. I told you the UCB Optom School had
problems.
Ray (electronics engineer)
William Stacy
writes:
>w...@ix.netcom.com(William Stacy ) wrote:
>
>>In <4r14u3$o...@agate.berkeley.edu> ken...@kabuki.EECS.Berkeley.EDU
(Ken A.
>>Nishimura) writes:
>>>
>>>
>.........................
>>>
>>>I think we have a Optics 101 problem. If the image is focussed
>>>in *front* of the retina, isn't this myopia? Hypermetropic eyes
>>>are optically too short, and the image focuses behind the retina.
>>>
>
>>Absolutely right. My 101 prof would be horrified at my ignoring that!
>
>Tell me you were recovering from a black widow or courgar bite. Or
>were you testing weed to see if it might be good for glaucoma? Guess
>you blew your chances of getting back on the Optometry Board.
Like I'd actually want more of that abuse...
Ray, while I've got your attention, let me set you straight on one
thing. Optometrists ARE trained in optics, of the physical, geometric,
ophthalmic and practical types. True, it doesn't stick for all of us,
but we sure as hell get a lot more of it thrown at us than does anyone
else on the planet.
Bill
Nick Jones
ken...@kabuki.EECS.Berkeley.EDU (Ken A. Nishimura) wrote:
Nick wrote
> : >It would appear that you are hypermetropic (far sighted) and that
> : >normally light focusses in front of your retina, however as the light
Well, I might have made an unforgiveable error but at least I took
someone with me!
> : Good answer, Nick.
What were you thinking, Bill?
>
> I think we have a Optics 101 problem. If the image is focussed
> in *front* of the retina, isn't this myopia? Hypermetropic eyes
> are optically too short, and the image focuses behind the retina.
>
1000 apologies for misleading the newsgroup, perhaps I should stick to
ocular motility questions.
Nick the Orthoptist
Ken A. Nishimura
: >In <4r14u3$o...@agate.berkeley.edu> ken...@kabuki.EECS.Berkeley.EDU (Ken A.
: >Nishimura) writes:
: >>
: >>
: .........................
: >>
: >>I think we have a Optics 101 problem. If the image is focussed
: >>in *front* of the retina, isn't this myopia? Hypermetropic eyes
: >>are optically too short, and the image focuses behind the retina.
: >>
: >Absolutely right. My 101 prof would be horrified at my ignoring that!
: Tell me you were recovering from a black widow or courgar bite. Or
: were you testing weed to see if it might be good for glaucoma? Guess
: you blew your chances of getting back on the Optometry Board. Check
: out *my* post on this subject. I haven't checked the date-and-time
: stamp on my post relative to Dr. Nishimura's, but I didn't copy any
: other "students'" papers around here. And I thought I knew which to
: copy--if I ever needed to. . . . I dunno. :-(
: >Glad to hear they're still teaching optics. Carry on!
: No doubt he sneaked over to Engineering to make sure the prof knew
: what he was talking about. I told you the UCB Optom School had
: problems.
: Ray (electronics engineer)
Ray -
I take offense at your using my posting to "bash" others. I've
sat through your antics in this group, mostly because
it wasn't worth answering. But, since my name is being used,
I am going to object.
True, Dr. Stacy made a mistake (or more accurately, didn't catch the
error made by Nick.) Tell me honestly you've never made a mistake.
I seriously doubt that you need to be under the influence of
arachnoid (specifically Latrodectus mactans) neurotoxins before you
made an error. Your disdain of the optometry profession is well known.
Isn't it time that you stopped telling us the obvious (that you hate ODs)?
Now, be honest -- would you rather see an OD that's made a few
mistakes, owned up to them, and learned from them, or one that's
so cocky that they won't admit to them. Think carefully.
False, I never was in Optometry school. I earned my B.S., M.S.,
and Ph.D. degrees in Electrical Engineering and Computer Sciences
at UC Berkeley, taught EE there and now employed in private
industry while continuing to interact with graduate students
at UCB. I am a registered Professional Engineer in the State
of California. Have I made errors in my field of expertise?
You bet. I made errors while teaching. The sharp students catch
me. I appreciate that (at least it keeps em awake). My profs
who taught me made errors. The best in the field made errors.
Engineering profs make errors too. So, please don't use the
Engineering profession as a tool to belittle others in the way
you seem to enjoy. I do believe that engineering is a noble
profession and that engineers in general are more knowledgable
than the population as a whole, but they are by no means perfect.
Just as there are good ODs and bad ODs, there are good EEs and
bad EEs. Consider that on the last PE exam, only 20.8% of the
EE applicants passed. I like to believe that Optometry as
a profession takes as much care in educating and practicing
the profession as Engineering does. Until I am shown otherwise,
I'll give them the benefit of the doubt. (Disclaimer: Yes,
one of my good friends is an OD -- UCB grad too!)
You ask then, why do I read this newsgroup? Because I am
a curious person, and I am also a "customer" of this profession.
I use this newsgroup as one of my sources of information. As
you can see, I don't take everything posted here as gospel, and
I review the postings I care about. If I see an error which I
view as significant, I point it out. I also try to bring the
theory of the answer into the discussion. My medical
knowledge comes from my own research, and looking at the
human body as a machine. I like to "reverse engineer"
the body as a tool to understand what's going on. It helps
me interact with my MD and OD -- we end up coming to the same
conclusion but by two different paths. Sort of a sanity
check. I am, in your words, being an educated consumer.
By the way, I find your response Re: Optometry Boards frivolous
and counterproductive. Not that your basic idea is bad, but the
way you present it is so distasteful, that it poisons the whole idea.
If you were serious about the idea, then you just took a step back.
If not, well, I'll chalk it up to "free speech."
I also do, on occasion, bring up points for discussion, which
are anti-status-quo. I do question my OD as to why she attempts
to charge me $110 for CLs that wholesale for $37.81 (AWP) and I can
get on the open market for $46. I believe that I brought that up
here in this newsgroup -- so no, I'm not a stooge for the profession
either.
Ray, you are no doubt an intelligent person. I noticed that you
posted a reply on this subject -- I haven't read your posting carefully,
so I can't comment. You know, it is possible for two people to catch an error
at the same time. So, don't worry about the timestamps (I haven't checked).
Even if your response was based on mine, what's wrong with that?
You *learned* something from others. Do you find that so offensive?
*I* learned the vast majority of what I know from the work of others.
Am I grateful? Yes. Am I defensive? No. (I do research in EE and related
fields, so I do figure *some* things out on my own :-)
I think you may have some good ideas in your head -- please expend
more effort in choosing the method of delivery. I request that,
to enhance the civility of this newsgroup. I demand that when you
use my name.
==Ken
Ph.D., PE, CP-ASEL, KO6AF
(for those who insist on wallpaper)
William Stacy
In <4r97t0$4...@agate.berkeley.edu> ken...@kabuki.EECS.Berkeley.EDU
(Ken A. Nishimura) writes:
>(...)
>I think you may have some good ideas in your head -- please expend
>more effort in choosing the method of delivery. I request that,
>to enhance the civility of this newsgroup. I demand that when you
>use my name.
>
I think that bit of advice and request could be well taken by everyone
on this group. Thanks for the fine discourse, Ken.
Bill
(also not fond of wallpaper, except for an occasional additional given
name glitch)
Edward De Gennaro
Richard Hemenger wrote:
>
> Fred Gurzeler wrote:
> >
> > If this post seems rather humorous, that's okay; I find it rather amusing
> > myself!
> >
> > Back in the days when I wore glasses, I would go diving from time to time
> > and discovered that I did not need to wear my glasses underwater. This,
> > of course, was wonderful because I didn't need to even think about
> > prescription goggles (I'll bet they're expensive!). The minute I got out
> > of the water, of course, I was back to being blind :-)
> >
> > Why is this? Is it because water refracts and reflects light so many
> > different ways that one of those rays is bound to enter my poor myopic
> > eyes and hit the retina just right? Why then, can't I look through a
> > fishtank and clearly see what's on the other side?
> >
>
Gentlemen:
Many people report that they see better underwater when they are diving
with a mask on. The reason for this is simple, there is a 1/3 increase
in the magnification of objects when you wear a diving mask underwater.
This occurs because the air trapped in the diving mask is separated
from the water by the diving mask face plate. The air in the mask has
an index of refraction of 1.00 while the water has an index of
refraction of 1.33. 1.30 divided by 1.00 multiplied by 100 equals 33%
magnification.
In practical terms, the 1/3 magnification is like walking 1/3 closer to
an object you can't see well. Sometimes, that's enough to see an object
more clearly. Big things are easy to see, little things are not.
That's the simple case of it all.
This is a very common comment with divers. BTW, this 1/3 increase in
magnification is also the cause of some "you should have seen the size
of that fish .... it was the biggest tuna I ever saw!!!!!" comments.
Ed De Gennaro
Opticianry Program
J. Sargeant Reynolds Community College
Richmond, Virginia
Raymond A. Chamberlin
w...@ix.netcom.com(William Stacy ) wrote:
>In <4r54hv$g...@sun.sirius.com> ra...@sirius.com (Raymond A. Chamberlin)
>writes:
>
..................
>
>Ray, while I've got your attention, let me set you straight on one
>thing. Optometrists ARE trained in optics, of the physical, geometric,
>ophthalmic and practical types. True, it doesn't stick for all of us,
>but we sure as hell get a lot more of it thrown at us than does anyone
>else on the planet.
Well, I guess I'm not supposed to kick someone when their down, right?
And Ken Nishimura has just recoiled in the embarassment of having
called a shot which happened to align with the same play as that of
consensual archnemisis here, who then flipped a card in Ken's own
professional suit, while tossing a snicker your way. I'll say a
little here the above subject and then bring the rest up in my
response to Ken.
There *is* a problem, from the public's standpoint, as to the gist of
the above, even though few of its members ever get the picture of what
this problem really consists of. All right, this boo-boo came about
in a specialized discussion about divers, and the world needn't get
too distracted by divers. (If they want to devolve back into the sea,
let them solve their own peculiar problems. ;-) ) And it's clear
here in this group how extended most of you guys are in knowldege of
physiology and pathology related to human eyes. But I, and the vast
majority of people go to optometrists, or would go to drugstores--if
they were allowed to sell our simpler needs (and let you be, to
compete with MDs on other matters)--just to get nonpathological vision
optimization by way of optical lenses--modified only slightly from
those you can buy by the handful from a surplus store, at least in the
case where they're used in spectacles
No, I don't contest .that UCB Optom students receive instruction in
optics. (I know, of course, what geometric and physical optics are,
but, I admit, I can only guess the scope of "ophthalmic" and
"practical" optics and would not know where to draw the line between
the two. Is the latter frame-benders' optics?) And my instruction
was only in the basics of the first two, and my application of it was
somewhat limited and is now distant.
But, as I've related before, I've been, in my life to eight or ten
optoms and ophthalms for simple refractions and found that they have
no feel, really at all, for what's going on optically; they just know
their trade as a more-or-less accepted ritual to be manually trained
in--and, oh yes, if the result doesn't seem right--always, "You have
to get used to it." As I've noted, I have had to get the right result
by cutting through the ritual. I don't know where some of these
people were educated, but three or four of my refractions were done at
the UCB Optom Clinic, and I was up there at other times, when I would
meet interns and students. Clearly there existed no curiosity in
these students as to how things ocular really worked; they merely saw
their training as a process to an acceptable source of income, hung to
their instructors' coattails and brushed off any clashing
considerations from clients or anywhere else.
But yes, students actually curious about the workings of eyes--in
terms of mathematics, physics and biology--would go batty in short
order, sitting in a clinical office flipping lenses in front of boring
people all day. So--from society's point of view--for uncomplicated
measurement for sensory prosthesis, I say let drugstore machines or
even home computers, along with mass merchandising, do it. Computers
tend not to reverse arithmetic signs without provocation. Let the few
who want to get into the eye-meat be part of the medical trade, not
necessarily joining the MD political band, but rather pushing
governments to let them show a different, better way--rather than "let
us play doctor too." Podiatrists did it.
Your last statement above is curious. I'm not sure what it is
supposed to get across. I say, if the bulk of your work is bonehead
optics, but this doesn't "stick", stick it in a computer program and
do something else that's either more humanistic or more challenging.
Of course, there's more and more optics "thrown" around "on the
planet" these days, but most of it is quitely sequestered in
laboratories or in reliable, obeisant boxes or networks, such as
storage devices and communications cables--put there by engineers
(ouch!), safe from the politics of personal service. ;-)
Ray (Hey, engineers stole it from physicists, Man.)
Ken A. Nishimura
Edward De Gennaro (edd...@i2020.net) wrote:
(stuff deleted -- I think we all know the original post by now).
: Gentlemen:
: Many people report that they see better underwater when they are diving
: with a mask on. The reason for this is simple, there is a 1/3 increase
: in the magnification of objects when you wear a diving mask underwater.
: This occurs because the air trapped in the diving mask is separated
: from the water by the diving mask face plate. The air in the mask has
: an index of refraction of 1.00 while the water has an index of
: refraction of 1.33. 1.30 divided by 1.00 multiplied by 100 equals 33%
: magnification.
I will respectfully disagree with your explanation.
The reasons for the effect you are describing has already been
correctly described before in previous posts. In summary, the
reason an "emmetropic in air" person cannot see well in water without
a mask is that the effectivity of the corneal lens is reduced due
to the higher index of refraction of water -- or more precisely, the
difference in the indices of refraction on either side of the
curved surface (lens) is less. This person will be hypermetropic
in water. (Recall, that this thread started with a myopic person,
who, under some circumstances will be able to see properly without
a mask due to fortuitous cancellation of two opposing effects.)
The reason the mask works is that it presents a *flat* surface between
the air/water interface (actually air/glass/water). A flat surface
cannot act as a lens, and a change in index of refraction leads to
reflection but not image magnification. The air space in front
of the eyes preserves the proper air/cornea interface for emmetropia.
If you still do not believe me, consider the following experiment.
Place a large block of glass/plastic on a newspaper -- be sure that
the block has flat sides (not a lens). The block represents
water -- easier to handle than a liquid. Now, let's assume you
chose a fine block of crown glass -- Nd = 1.523. By your logic,
since the air in front of your eyes has Nd of 1.00, but the block
of glass (representing water) has a Nd of 1.523, there will be
"1.523 divided by 1.000 multiplied by 100% or 52.3% magnification."
I doubt that you will see this effect in real life.
(If you choose to use water, just use a rectangular aquarium tank
for the experiment -- you can even put the test object IN the
water to more carefully reproduce the situation in question).
==Ken
William Stacy
In <31D9AD...@i2020.net> Edward De Gennaro <edd...@i2020.net> writes:
>
>
>Many people report that they see better underwater when they are diving
>with a mask on. The reason for this is simple, there is a 1/3 increase
>in the magnification of objects when you wear a diving mask underwater.
> This occurs because the air trapped in the diving mask is separated
>from the water by the diving mask face plate. The air in the mask has
>an index of refraction of 1.00 while the water has an index of
>refraction of 1.33. 1.30 divided by 1.00 multiplied by 100 equals 33%
>magnification.
Ed:
You're almost right. If the mask has a curved surface, there will be
magnification effects due to the differences of indices of refraction
of the surfaces.
However, if the mask is flat, like most I've seen, there is *no*
appreciable difference in magnification across the mask surfaces, at
least according to Snell and his friends.
Bill
Ed Sheridan
> gurz...@aol.com (Gurzeler) wrote:
>
> >If this post seems rather humorous, that's okay; I find it rather amusing
> >myself!
>
> >Back in the days when I wore glasses, I would go diving from time to time
> >and discovered that I did not need to wear my glasses underwater. This,
> >of course, was wonderful because I didn't need to even think about
> >prescription goggles (I'll bet they're expensive!). The minute I got out
> >of the water, of course, I was back to being blind :-)
>
> >Why is this? Is it because water refracts and reflects light so many
> >different ways that one of those rays is bound to enter my poor myopic
> >eyes and hit the retina just right? Why then, can't I look through a
> >fishtank and clearly see what's on the other side?
>
> optics than that of air, and thus the aberrations in your eyes' optics
> do not show up as much. More specifically, I suspect you wear glasses
> for myopia, and the higher index of the water results in a longer
> focal length from your eyes' optics, so that you see to a further
> distance. Of course, in the case of the fish tank, there is air
> between your eyes and the tank. For the effect, the water has to be
> essentially in contact with your eyes.
>
> >If I am correct about the refractive power of water, does it follow that
> >people with dry eyes often have more vision problems than people with
> >nice, moist eyes?
Does anyone think that the pressure from the dive against his eyes could
be reshaping them just enough for him to see well? Just a thought.
Ed
Raymond A. Chamberlin
ken...@kabuki.EECS.Berkeley.EDU (Ken A. Nishimura) wrote:
>
......................
>
>Ray -
> I take offense at your using my posting to "bash" others. I've
>sat through your antics in this group, mostly because
>it wasn't worth answering. But, since my name is being used,
>I am going to object.
I don't really want to rebut this long post of resentment; it has it's
legitimate concerns. However, I'd like to comment that it has to be
taken in part as youthful overreaction, maybe partly as a result of
not being privy to some light comments that passed by e-mail between
Bill and me. But beyond its excessiveness, some persons may have
noted its purported impetus and justification might, in fact,not be
quite as clear-cut as set out for us to accept. I think the issues
should be submitted to an equitological analysis, a scientific view of
the equitation, or hosemanship, of what went on here: Who should get
on his high horse and who should pony up. Less metaphorically, the
actual acts and motives here should be separated and set in
perspective.
The Internet was designed for passage of information, and that is the
prime mode that interests me. It does curious things to sociality,
some maybe good, some rather bad. I think it is a poor substitute for
real-life sociality, and though I may go with it in that mode at
times, I am sure to drop back to cold information transfer much of the
time. One attribute of electronic forums is that a participant
doesn't have to have a sixth sense of split-second conversational
timing to gain the floor, and one is not obliged to wade through a
long boring topic in order to wedge in something he finds of interest.
Another attribute is that the age, and of course, other physical
characteristics of a participant are not inherently available to those
in attendence. The communicator is as his/her symbol structures
elicit from the priorities of the several recipients..
Mr./Dr. Nishimura has ended his letter with his "wallpaper", as he
terms it (I have no idea what CP-ASEL is.). He has clearly endured a
stiff program of studies, all of it at UCB, where additionally he
taught his subject, electrical engineering. From the Net, we also
find that he did some research there in analog integrated-circuit
research, apparently leaving that institution around the end of 1994,
and is now doing research in low-power analog CMOS circuits for signal
processing at the Deer Creek facility of Hewlett-Packard, Palo Alto.
Interestingly, he seems to be known as a "Grad Student Emeritus", a
designation of which I had never before heard. (A talk and paper,
linked to his page at H-P are among the missing. Did they reveal
trade secrets or what?) Mr. Nishimura's excelent teaching abilities
are also well demonstrated in two extensively informing
Internet-archived forum pages on Ni-Cd batteries, one a FAQ. This
knowledge apparently arose from his amateur-radio avocation. Given
the expected time scale and the mode of expression set down in the
post, I would gather Mr./Dr. Nishimura to be around 30 years of age,
give or take 2.
So, from this very respectable but not really lofty perch, he is
offended at my "using [his] post to 'bash' others." But immediately
it is made very clear that his *actual* shock was that of his sudden
tie-in to a person who had repeatedly posted in conflict with many of
the members of the quasi-owner profession of the newsgroup, whose ire
he had thereby drawn.
First, what actually did go on? Nick, the Australian orthoptist,, in
answer to a diver's article, posted a refractive diagnosis directly
conflicting in ametropic sign, based on a situation involving a
fundamental optical relationship dependent on the relative refractive
indices in an air-water switching, in an interface to the human eye's
corneal optical medium. Then Bill Stacy, a conventional optometrist,
who's daily professional tasks center on such optical relationships,
reviewed Nick's post and praised it, overlooking the reversed
ametropic diagnosis. Then Ken, the teacher (but not of optics, though
no doubt of solid wide-scope engineering knowledge, as gauged by his
PE status), pointed out the error in a post of his.
Now, how did this young person of considerable stature, who now rails
at me for involving his name in a subsequent post of mine that he
labels a "bashing"--one which post teases Bill a little for his
oversight--present this discovery? He said, "I think we have a [sic]
Optics 101 problem." Now, if one wants to claim having a little fun
with someone who overlooked a mistake directly underpinning his stock
in trade is "bashing"--should that one not avoid the smack-in-the-face
description "Optics 101 problem"? And later on, Nick jests something
like, "Well, at least I took one with me." Ken doesn't dress down
Nick for that snipe. Obviously, Ken's big concern lies not in simply
the instant pin-sticking, but in a fair of getting associated in
general with my other views and antics on this newsgroup, through his
suddenly discovered alignment with 1) a diagnosis I gave that was
opposite to that of two ophthalmic types, and 2) a profession in
common with me.
The actual sequence was: After Ken's correcting post, but before I
reloaded my newsreader to see Nick's and his posts, I posted in
response to the same diver's article, indicating the correct sense of
ametropia. Then I read Nick's and Bill's posts. Immediately I
thought, well somehow, I blew it. Contray to Ken's view that I smugly
feel I'm never wrong, on things like that--where, say, the sense of
something can get reversed, and there aren't a lot of simply checks on
it--I frankly don't have a lot of confidence that I haven't made a
mistake. But I couldn't reconcile Bill's answer. Then I read Ken's
correcting post, where he worded the problem and its answer very well
(as befitted the fine teacher that he is), and realized that the other
two had, indeed, goofed.
In light of the above, and in the context of having joked around a lot
with Bill, both in s.m.v and by e-mail--*as well as* seriously
knocking a number of things optometric, in jousts with him--I posted
my roasting article, which referenced Ken's corrective post. I
fantasized (not knowing he *was* an EE and not an optometric type) an
extraophthalmic source of correct answer for Ken which aligned to
mine and noted that discipline after my signature, just to impose an
army foreign to the ophthalmic world which had its hands on right
answers.
I say Ken's concern was not that his innocent name had suddently
appeared in a "bashing" of an optometrist, but that he suddenly
reflected on the fact that he had just jabbed, none too subtly, a
basic-optometry correction into an optics-problem discussion of two
optometrists in this newsgroup who, with other optometrists there, had
been taking continual flak from a person who had been blackballed for
such by some of them--and who, as a result, he wished not to be
aligned with--but that that person now was claiming the same
profession as his, as well as an answer to the subject optics problem
which happened to align to his correct analysis of that problem.
Basically, he felt chagrined that his blast correcting this very basic
optical faux pas, though correct and in line with his teaching role
and his natural instincts to view human bodily functions in terms of
basic physical laws, had suddenly turned into something that had put
him in double alignment with someone of whose style he greatly opposed
and who was politically wrong for him to be aligned with in regard to
interaction with optometrists. "Holy horrors, *I* didn't do it, *Ray*
did it! He used my answer; he used my profession; he used my name.
Yikes! And he's the enemy; he hates optometrists! These s.m.v.
optoms and my friend will never forgive me! (My optometrist will
desert me and my vision will suffer. ;-) ) Woe is me!" *THAT* is
what his railing here is all about.
>True, Dr. Stacy made a mistake (or more accurately, didn't catch the
>error made by Nick.) Tell me honestly you've never made a mistake.
Well, back in 1931. . .I got born--too long before the transistor was
invented. Bad idea, but it was the last mistake I ever made. ;-)
The issue here, however, is hardly whether *I* make mistakes. I made
a very bad one the other day: I was quizzed in a job interview as to
the effect on the gain of an op-amp, of a shunt resistor at its input,
where the signal source had a fair-sized series resistor. Of course,
it has no effect unless it's extremely low in value. But at that
moment, without an early-age imprint (even started with tubes), some
basic circuit thought brought me the wrong answer. I've designed a
lot of analog board circuitry some time back, but I've spent more time
on digital circuits. Anyhow, the wrong answer sort killed any idea
that designing with op-amps was second-nature with me and that I'd
just finished such a design yesterday. That mistake is worse, of
course, than what Bill did, so use that against me. However, I don't
see that my making mistakes in something else detracts from numerous
points I've made here against a number of ophthalmic bad habits and
shams--which kick science and public ethics in the face.
>I seriously doubt that you need to be under the influence of
>arachnoid (specifically Latrodectus mactans) neurotoxins before you
>made an error.
Well, here's where you weren't privy to something. This wasn't just
an attempt to think of some wildly disastrous condition, anything less
than which could not be considered a valid excuse for Bill's error
here. We had e-mailed, among other things, casual comments about
mountain lions, which are not so uncommon in his area, near where a
fatal attack occurred a year or two ago. Also, I believe, as a
humorous excuse for not checking files in his garage for a point of
discussion of ours, Bill had commented that the garage was full of
black widow spiders. (Is this comment an excuse to adverise your
knowledge of spider venoms? ;-) )
>Your disdain of the optometry profession is well known.
>Isn't it time that you stopped telling us the obvious (that you hate ODs)?
I hate stuff that doesn't work, doesn't compute or isn't very fair to
people. There's an exceptional amount of all three in optometry and
ophthalmology and the rest of medicine.
>Now, be honest -- would you rather see an OD that's made a few
>mistakes, owned up to them, and learned from them, or one that's
>so cocky that they won't admit to them. Think carefully.
Do you really think I was condemning Bill in particular for this
particular amusing faux pas. My main concern is systematic technical
procedures and econo-politico-legal games that make a lot of
optometry, etc. "funny". Bill's apparently a mixed bag on some of
this. My concern is that *collectively* these people won't admit to
the Mickey Mouse things that go on. The same stance as you find in
the tobacco industry, the legal-judicial industry and a lot of other
places. Hey, I hate all kinds of things. ;-)
>False, I never was in Optometry school. I earned my B.S., M.S.,
>and Ph.D. degrees in Electrical Engineering and Computer Sciences
>at UC Berkeley, taught EE there and now employed in private
>industry while continuing to interact with graduate students
>at UCB. I am a registered Professional Engineer in the State
>of California.
Sounds great. You didn't post much. I did take you for someone
connected with the UCB Optom School. You've gone up lotsa points on
my scale. ;-) I know, you have conflicting feelings on such
subjects.
>Have I made errors in my field of expertise?
>You bet. I made errors while teaching. The sharp students catch
>me. I appreciate that (at least it keeps em awake). My profs
>who taught me made errors. The best in the field made errors.
>Engineering profs make errors too.
So if we make errors, we are sure to become the best in our field,
right?
>So, please don't use the
>Engineering profession as a tool to belittle others in the way
>you seem to enjoy.
You've said more about engineering here than I have in all my posts.
My only point about engineering is that its use of science has to
remain pretty intellectually on the level, or bridges fall down.
Inanimate matter doesn't yield to politics and you can't complain that
the patient brought you a hopeless case or avoid an autopsy.
>I do believe that engineering is a noble
>profession and that engineers in general are more knowledgable
>than the population as a whole, but they are by no means perfect.
Engineering is a no-bull profession, but EEs become obsolete awfully
fast. But then the nearly perfect engineer works very hard to get
himself replaced. Physicians, in very tight political formation, work
very hard to maintain the status quo for economic reasons--and then
they die of boredom on the golf course.
Now, here I tend to disagree with you on logical grounds. How, pray
tell, can the rather limited number of engineers on this planet know
more than "the population as a whole" (which includes engineers)?
Now, if you had said "the population as a whole, less engineers", I
might agree with you. ;-) But if you simply mean a typical
engineer knows more than your average person, that doesn't do much for
me. Are you making mistakes to show the optometrists here that
engineers are only human (despite the fact that they reverse-engineer
their bodies as machines)? Well, if EECSs have a CS side, reconsider
that engineers know more from bottom up, while maybe old
Altzheimer's-headed Ronald Reagan knew more how to wreck the country
quickly from top down. While you're next reverse-engineering the
brain, see if you can find out if the hardware isn't kind of
topologically split to handle Cartesion dualism. I mean, how else can
a processor handle others of its level of complexity? The latter task
cannot be done alone from the bottom up.
I read your statements here and they show up your problem: You
recognize systematic defects in the doings in optometry, etc., but you
fear any sort of 'bigot' label's getting attached to you from any
urging that you might do as to an engineering mode of application of
science's being impressed on optometry, etc. So on the surface you
feign that "everything is beautiful in its own way." (An engineering
mode of using science is, after all, only honest and faithful use of
it, do not so much to the integrity of the engineer as to the
hopelessness of using it otherwise in engineering.)
>Just as there are good ODs and bad ODs, there are good EEs and
>bad EEs.
I'm sooooooooooooooooo sick of that politically correct generalization
about any two things in the world that I'm about to. . . Some groups
of thingies have more bad thingies than other groups of thingies do.
That's a corollary of Murphy's Law. So Murphy's a bigot. Hates
anybody who isn't Irish.
>Consider that on the last PE exam, only 20.8% of the
>EE applicants passed.
So that means those who passed are pretty damn good, right? But what
about me? I never took it. Does that make me good or bad? My job
didn't deal directly with the public and I didn't have anything to
prove. Now look, maybe only 70% of the students entering an
engineering program graduate. That means that all the PE-exam
applicants weren't so bad to begin with. Oh, wrong! Even those that
passed the PE exam form one of those groups of which some have to be
"good engineers" and some "bad". You never win--just another
corollary of Murphy's Law--the Law of Insuperable Defectiveness. :-(
Well, a lot higher number of law graduates pass the Bar, right? And
almost all of them can keep at it until they pass it in the seventh
attempt, right. That means *most* lawyers are disgusting. You see,
if you don't just simply crank out good lenses of all kinds from a
factory and stick them on the shelf, but instead, pass laws that
prevent that and allow you to tell the patient he/she "just has to get
used to your prescription, right or wrong," you can make words come to
any kind of conclusion you want. Murphy's last law.
>I like to believe that Optometry as
>a profession takes as much care in educating and practicing
>the profession as Engineering does.
Notice that "like" in there. You would no doubt "like" me to believe
that you *believe* what you're saying, but it's clear that you *don't*
really believe here what you'd like to, and that's what bothers you,
Cousin. OK, I'd like to believe what you like to believe in this
instance, but I don't. So how do you compare practicing engineering
and practicing optometry anyhow? (Please don't disinter Snellen to
invent a common scale. ;-) )
>Until I am shown otherwise,
>I'll give them the benefit of the doubt.
OK, but on that basis, you have to allow--given the fact that I,
having lived longer, have been shown otherwise (as heretofore
evidenced), i.e., *educated*--that my views are at least as valid as
your naïve views.
>(Disclaimer: Yes,
>one of my good friends is an OD -- UCB grad too!)
Guilt by association, definitely.
>You ask then, why do I read this newsgroup? Because I am
>a curious person, and I am also a "customer" of this profession.
Same here.
>I use this newsgroup as one of my sources of information. As
>you can see, I don't take everything posted here as gospel, and
>I review the postings I care about. If I see an error which I
>view as significant, I point it out. I also try to bring the
>theory of the answer into the discussion. My medical
>knowledge comes from my own research,
Medical research? Or just silicon-circuit research that produces
knowledge applicable to medicine?
>and looking at the
>human body as a machine.
There are a lot of other people who will hate you for that, but that's
exactly what produces useful medicine. And understanding of human
discomforts doesn't just come from biology; a lot of direct physics is
applicable, but MDs mostly don't want to work their jobs that way.
>I like to "reverse engineer"
>the body as a tool to understand what's going on.
Well, perhaps here you've raised the philosophical question as to
whether one can "reverse engineer" something that has only evolved.
(We won't worry about the theory of The Big Engineer in the Sky.)
Do you have a human-genome program yet?
>It helps
>me interact with my MD and OD -- we end up coming to the same
>conclusion but by two different paths.
I would like to see that, because I've found that MDs approach
problems in ways that never could reach conclusions that engineers
reach by their approaches. I'll go so far as to say that *my*
conclusions as to my medical and optometric needs have
proved out vastly more often than those of the MDs treating me. I
quite frankly don't believe what you say here. You are simply being
politically correct.
>Sort of a sanity
>check.
Who gets the straightjacket on a parity failure?
>I am, in your words, being an educated consumer.
I don't recall having used that term.
>By the way, I find your response Re: Optometry Boards frivolous
>and counterproductive. Not that your basic idea is bad, but the
>way you present it is so distasteful, that it poisons the whole idea.
>If you were serious about the idea, then you just took a step back.
>If not, well, I'll chalk it up to "free speech."
If anything is simple and cheap, this paragraph certainly is. I
presented the laws as they stand. You admit "the basic idea isn't
bad". So present the idea in your form; don't just post long
complaints about how others do in respect to what you don't do at all,
but have similar thoughts about. I'd say, your talking about your
tastes is "free speech". There's always someone talking about his
tastes in Sproul Plaza--and how, if you don't see it his way, you'll
roast in Hell. You could argue that I shouldn't have included a
demonstration of the sloppy inconsistency of these statutes along with
my objections to their disruptiveness in an open society, but others
would disregard that and complain that I didn't present case law on
the subject. So why don't you present the case law, of which there
probably isn't much.
>I also do, on occasion, bring up points for discussion, which
>are anti-status-quo. I do question my OD as to why she attempts
>to charge me $110 for CLs that wholesale for $37.81 (AWP) and I can
>get on the open market for $46.
So, you only challenge corruption when you're about to lose a few
lousy bucks out of your pretty reasonably fed pocket. Am I supposed
to become overwhelmed by that sort of social responsibility?
>I believe that I brought that up
>here in this newsgroup -- so no, I'm not a stooge for the profession
>either.
*I* don't recall having read about that in this newsgroup.
>Ray, you are no doubt an intelligent person. I noticed that you
>posted a reply on this subject -- I haven't read your posting carefully,
>so I can't comment.
Your response was, of course, worded much better.
>You know, it is possible for two people to catch an error
>at the same time. So, don't worry about the timestamps (I haven't checked).
Well, I'm really worried; somebody might think I cheated. ;-) Are
you really this far out to lunch? I was just playing with Bill. I
posted *after* all of you guys--but before I downloaded your
responses.
>Even if your response was based on mine, what's wrong with that?
*Wrong* with it? The reference was just to the fact of two
independent non-optometrist correct responses to two optometrist
*wrong* responses (although not independent).
>You *learned* something from others. Do you find that so offensive?
"Do I find learning something from others offensive?" Come off it.
Gimme a break. Teachers are funny, but not *that* funny.
>*I* learned the vast majority of what I know from the work of others.
Who doesn't, for cryin' out loud? I certainly wouldn't claim
otherwise for myself.
>Am I grateful?
Well, I suppose H-P might not pay you if you hadn't gone and "stolen"
that knowledge. ;-)
>Yes. Am I defensive? No. (I do research in EE and related
>fields, so I do figure *some* things out on my own :-)
Bully for you. Isn't that what they're paying you for? If you need
help figuring this post out, don't call me; call your optometrist.
>I think you may have some good ideas in your head -- please expend
>more effort in choosing the method of delivery. I request that,
>to enhance the civility of this newsgroup.
If you compare this group to other newsgroup in respect to civility, I
think you'll find this group more civil than the average one.
>I demand that when you
>use my name.
I'll keep your name out of my posts after this one, but I think, in
any case, you'll be judged almost completely by what is posted over
*your* name, not what is contained in another's post which happens to
contain your name.
Now, you complain of my "style". Does style run independent of
political discretion? You hint that you might have some concerns
about optometry, etc. that run a little a long the lines of some I've
expressed. So why don't you show me your "style" on these or others
of your choosing. I think your concern is mostly over evidence here
of espousing something that might turn off an employer or health-care
practitioner of yours. I think you're afraid to go after any issue
slightly in conflict with orthodox optometry, in *any* style, for fear
of the wrong person's reading it. Well, you're right; what's written
here is for all in the world to read. The search engines now display
archived copies of your posts, which may last for a couple of months.
Your posts are in the public domain. Who's to prevent a business from
keeping them indefinitely and selling CD-ROMs full of such stuff to
employers--perhaps yours or a prospective one of yours? Who's to keep
the health-care people from keeping such a log?
I think some things around here should maintain some intellectual
integrity. Some others, integrity of public ethics. Perhaps the
Vatican has style, but does its flock skip rope with it? If you think
my humor is aqueous, you can stick it in your eye. Where's the beef?
Ray
.John Watts.
Raymond A. Chamberlin wrote:
>
> ken...@kabuki.EECS.Berkeley.EDU (Ken A. Nishimura) wrote:
>
> >
> ......................
> >
> >Ray -
>
> > I take offense at your using my posting to "bash" others. I've
> >sat through your antics in this group, mostly because
> >it wasn't worth answering. But, since my name is being used,
> >I am going to object.
> >
> integrity. Some others, integrity of public ethics. Perhaps the
> Vatican has style, but does its flock skip rope with it? If you think
> my humor is aqueous, you can stick it in your eye. Where's the beef?
>
> Ray
Ray,
Who is listening Ray?
You take yourself too seriuosly Ray. Who cares what you say Ray?
We know you're just an electrician with an alter[d]ego.
But be carefull Ray lest you poke yourself in the wrong eye and
completely blind yourself.
Take your own advice and do some "reverse engineering" on yourself. You
may, per chance, discover from which Lab you were spawned.
John
Raymond A. Chamberlin
Edward De Gennaro <edd...@i2020.net> wrote:
>Richard Hemenger wrote:
>
......................
>
>Gentlemen:
>Many people report that they see better underwater when they are diving
>with a mask on. The reason for this is simple, there is a 1/3 increase
>in the magnification of objects when you wear a diving mask underwater.
> This occurs because the air trapped in the diving mask is separated
>from the water by the diving mask face plate. The air in the mask has
>an index of refraction of 1.00 while the water has an index of
>refraction of 1.33. 1.30 divided by 1.00 multiplied by 100 equals 33%
>magnification.
>In practical terms, the 1/3 magnification is like walking 1/3 closer to
>an object you can't see well. Sometimes, that's enough to see an object
>more clearly. Big things are easy to see, little things are not.
>That's the simple case of it all.
>This is a very common comment with divers. BTW, this 1/3 increase in
>magnification is also the cause of some "you should have seen the size
>of that fish .... it was the biggest tuna I ever saw!!!!!" comments.
Well, this time I've seen the two above responses to the post I
respond to here. Of course, I agree with the first, that of the
gentleman from H-P. I hope no opinions I've had on other subjects
cause him any difficulty as a result of our consensus here.
As to Dr. Stacy's comments, I would just add that to magnify, the face
of the mask would have to be not just "curved" but have its two sides
curved with different effective radii (or only one side of 0 curvature
(flat)). Parallel curved surfaces would only introduced minor
distortion, as curved windshields do.
I would say that putting an object in a broad jar with a relatively
flat bottom (these are not too uncommon) and filling it with water is
the easiest manner in which to demonstrate the lack of magnification
of such an object in cases where the air-glass/plastic-water
interfaces are flat and parallel. Where the surfaces between the
materials of different indices of refraction are parallel, parallel
rays from different parts of an object each experience the same total
total bending, and so no magnification occurs, only lateral
translation of an object's actual position occurs in cases where it is
viewed at an angle to the surfaces. Fish stories are fishy because
that's what fish stories are--even if they aren't about fish. Not
believing that psychology is a science, I question that science has an
answer to fish stories, and I reel-ly wouldn't feed you a line. :-)
Ray
William Stacy
In <4rvge8$e...@sun.sirius.com> ra...@sirius.com (Raymond A. Chamberlin)
writes:
>As to Dr. Stacy's comments, I would just add that to magnify, the face
>of the mask would have to be not just "curved" but have its two sides
>curved with different effective radii (or only one side of 0 curvature
>(flat)). Parallel curved surfaces would only introduced minor
>distortion, as curved windshields do.
Now my optics 101 prof would roll over if I let an error like that one
go by. (Is this a troll?)
Assuming your hypothetically curved diving mask face-plate is of a
higher index of refraction than that of water (I can't think of any
sturdy transparent solid that isn't), there WILL be a significant
refractive result from a curved interface, accompanied by significant
magnification, even if the two surfaces of said face plate are equally
curved, unless BOTH sides of the face plate are water-filled (not too
comfortable for most of us).
Simple "ray" tracings will show that, as will mathematical calculations
using Snell's law and it's derivatives. The situation is remarkably
analogous to that of the human cornea, which has two surfaces which are
roughly parallel and which impart MOST of the eye's refractive power
BECAUSE one surface normally interfaces with air while the other does
so with water.
I'll bet fish corneas aren't biconvex, either.
Bill
Raymond A. Chamberlin
".John Watts." <kre...@squirrel.com.au> wrote:
>
.....................
>
>Ray,
>Who is listening Ray?
>You take yourself too seriuosly Ray. Who cares what you say Ray?
>We know you're just an electrician with an alter[d]ego.
>But be carefull Ray lest you poke yourself in the wrong eye and
>completely blind yourself.
>Take your own advice and do some "reverse engineering" on yourself. You
>may, per chance, discover from which Lab you were spawned.
Hey, I bet you learned this sort of sales technique in advertising
school, didn't you? Why should anybody buy Computer-Eyes glasses,
when everyone knows that computers don't even have eyes? See ya.
Ray
.Neil Royle.
> Hey, I bet you learned this sort of sales technique in advertising
> school, didn't you? Why should anybody buy Computer-Eyes glasses,
> when everyone knows that computers don't even have eyes? See ya.
>
> Ray
Oh Ray, only you could have such a pathetic come back.
Well Ray, it's been fun but gotta go now.
Score: Ray -200 rest of the world +1000
See ya round Ray.
Neil the ray buster.
Raymond A. Chamberlin
w...@ix.netcom.com(William Stacy ) wrote:
Touché!
R(edface)ay
\_ (tail dragging)
>I'll bet fish corneas aren't biconvex, either.
Another project for Stacy Labs. (Motto: "If we don't know it, we'll
fish for it.)
Ray
Raymond A. Chamberlin
".Neil Royle." <kre...@squirrel.com.au> wrote:
>
..................
>
>Oh Ray, only you could have such a pathetic come back.
That wasn't a come-back; that was a go-away. Have a good vacation.
Ray