Doubt in activity question

[Pranjal Singh]

I have doubt in week2 activity 8 question why we are not taking the height of both the  thief

[Malabika Guha Mustafi]

To get the range perfectly we need to consider the head of thief 1 and leg of thief 2. 

The torch light rays actually give  range of slopes (consider , the range from m1 to m2, where m1 is the slope of left most ray and m2 is the slope of right most ray  ).

if range of  slope of  thief 1 line(considering head)  and slope of thief 2(considering leg)  compare with range of m1 and m2  we can definitely say who can be visible [ when m1 is greater than head of first thief then it is confirmed that the thief is not within m1 -m2 range so not visible. But if we consider the feet of first thief then there is a possibility that feet slope may be lesser than m1 but other portion of thief's 1 body is within the range so visible. so, head of first thief is optimum position.]

 Again if we consider the 2nd thief's head for calculating slope of line we may miss number 2, there is a chance of miscalculation.

[when m2 is less than 2nd thief's leg , it is confirmed 2nd thief is out of range so not visible,. but if we consider his head then there is a possibility that head may be out of range but other's part may be within range and visible. so leg  position is optimum for second thief.]

[subhajit POD]

Try to observe that those are the optimal positions. 

To see both of them in the same cone of light it is enough to see the head of the thief  who is standing in the front and the feet of the thief who is standing in the back. 

Best

Subhajit