Electromagnetic Waves Lab Manual

[Nu Alessio]

Radiowaves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, gamma rays, and cosmic rays are the different regions of the electromagnetic spectrum. They are arranged in the order of decreasing frequency and rising order of wavelength.

We hope you enjoyed studying this lesson and learned something cool about the Electromagnetic spectrum! Join our Discord community to get any questions you may have answered and to engage with other students just like you! We promise, it makes studying much more fun!?

The site is secure.

The ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

The Food and Drug Administration (FDA) has regulated the manufacture of microwave ovens since 1971. Microwave oven manufacturers are required to certify their products and meet safety performance standards created and enforced by the FDA to protect the public health. Based on current knowledge about microwave radiation, the Agency believes that ovens that meet the FDA standard and are used according to the manufacturer's instructions are safe for use.

Microwave ovens are a convenient means to heat food and are generally safe when used correctly. Microwave ovens heat food using microwaves, a form of electromagnetic radiation similar to radio waves. Microwaves have three characteristics that allow them to be used in cooking: they are reflected by metal; they pass through glass, paper, plastic, and similar materials; and they are absorbed by foods.

A device called a magnetron inside the oven produces microwaves. The microwaves reflect off the metal interior of the oven and cause the water molecules in food to vibrate. This vibration results in friction between molecules, which produces heat that cooks the food.

Microwaves are non-ionizing radiation, so they do not have the same risks as x-rays or other types of ionizing radiation. But, microwave radiation can heat body tissues the same way it heats food. Exposure to high levels of microwaves can cause skin burns or cataracts. Less is known about what happens to people exposed to low levels of microwaves.

To ensure that microwave ovens are safe, manufacturers are required to certify that their microwave oven products meet the strict radiation safety standard created and enforced by the FDA.

Microwave energy will not leak from a microwave in good condition. A damaged microwave oven may present a risk of microwave energy leaks. Contact your microwave's manufacturer for assistance if your microwave oven has damage to its door hinges, latches, or seals, or if the door does not open or close properly.

Microwaves are a form of "electromagnetic" radiation; that is, they are waves of electrical and magnetic energy moving together through space. Electromagnetic radiation spans a broad spectrum from very long radio waves to very short gamma rays. The human eye can only detect a small portion of this spectrum called visible light. A radio detects a different portion of the spectrum, and an X-ray machine uses yet another portion.

Visible light, microwaves, and radio frequency (RF) radiation are forms of non-ionizing radiation. Non-ionizing radiation does not have enough energy to knock electrons out of atoms. X-rays are a form of ionizing radiation. Exposure to ionizing radiation can alter atoms and molecules and cause damage to cells in organic matter.

Microwaves are used to detect speeding cars and to send telephone and television communications. Industry uses microwaves to dry and cure plywood, to cure rubber and resins, to raise bread and doughnuts, and to cook potato chips. But the most common consumer use of microwave energy is in microwave ovens. Microwaves have three characteristics that allow them to be used in cooking: they are reflected by metal; they pass through glass, paper, plastic, and similar materials; and they are absorbed by foods.

Although heat is produced directly in the food, microwave ovens do not cook food from the "inside out." When thick foods are cooked, the outer layers are heated and cooked primarily by microwaves while the inside is cooked mainly by the conduction of heat from the hot outer layers.

Microwave cooking can be more energy efficient than conventional cooking because foods cook faster and the energy heats only the food, not the whole oven compartment. Microwave cooking does not reduce the nutritional value of foods any more than conventional cooking. In fact, foods cooked in a microwave oven may keep more of their vitamins and minerals, because microwave ovens can cook more quickly and without adding water.

Glass, paper, ceramic, or plastic containers are used in microwave cooking because microwaves pass through these materials. Although such containers cannot be heated by microwaves, they can become hot from the heat of the food cooking inside. Some plastic containers should not be used in a microwave oven because they can be melted by the heat of the food inside. Generally, metal pans or aluminum foil should also not be used in a microwave oven, as the microwaves are reflected off these materials causing the food to cook unevenly and possibly damaging the oven. The instructions that come with each microwave oven indicate the kinds of containers to use. They also cover how to test containers to see whether or not they can be used in microwave ovens.

The FDA received reports in the past of serious skin burns or scalding injuries around people's hands and faces as a result of hot water erupting out of a cup after it had been overheated in a microwave oven. Super-heated water (water heated past its boiling temperature) does not appear to be boiling and occurs when water is heated by itself in a clean cup. If super-heating has occurred, a slight disturbance or movement such as picking up the cup, or pouring in a spoon full of instant coffee, may result in a violent eruption with the boiling water exploding out of the cup. Adding substances such as instant coffee or sugar before heating greatly reduces this risk.

Users should closely follow the precautions and recommendations provided in the microwave oven instruction manuals, specifically regarding heating times. Users should make sure that they do not exceed the recommended heating times when determining the best time settings to heat water to the desired temperature.

Through its Center for Devices and Radiological Health (CDRH), the FDA sets and enforces standards of performance for electronic products to assure that radiation emissions do not pose a hazard to public health.

A Federal standard (21 CFR 1030.10) limits the amount of microwaves that can leak from an oven throughout its lifetime to 5 milliwatts (mW) of microwave radiation per square centimeter at approximately 2 inches from the oven surface. This limit is far below the level known to harm people. Microwave energy also decreases dramatically as you move away from the source of radiation. A measurement made 20 inches from an oven would be approximately 1/100th of the value measured at 2 inches from the oven.

The standard also requires all ovens to have two independent interlock systems that stop the production of microwaves the moment the latch is released or the door is opened. In addition, a monitoring system stops oven operation in case one or both of the interlock systems fail.

All ovens must have a label stating that they meet the safety standard. In addition, the FDA requires that all ovens have a label explaining precautions for use. This requirement may be dropped if the manufacturer has proven that the oven will not exceed the allowable leakage limit even if used under the conditions cautioned against on the label.

Consumers should take common sense precautions regarding handling of hot foods and beverages. For more safety recommendations see the section of this page titled: Tips on Safe Microwave Oven Operation.

Most injuries related to microwave ovens are the result of heat-related burns from hot containers, overheated foods, or exploding liquids. Most injuries are not radiation-related. That said, there have been very rare instances of radiation injury due to unusual circumstances or improper servicing. In general, microwave oven radiation injuries are caused by exposure to large amounts of microwave radiation leaking through openings such as gaps in the microwave oven seals. However, the FDA regulations require that microwave ovens are designed to prevent these high-level radiation leaks.

If you suspect a radiation safety problem with your microwave oven, you may contact the microwave oven manufacturer. Manufacturers who discover that any microwave ovens produced, assembled, or imported by them have a defect or fail to comply with an applicable Federal standard are required to immediately notify FDA. In addition, manufacturers/importers are required to report all accidental radiation occurrences to the FDA, unless the incident is associated with a defect or noncompliance that has previously been reported (21 CFR 1002.20).

Manufacturers of electronic radiation emitting products sold in the United States are responsible for compliance with the Federal Food, Drug and Cosmetic (FD&C) Act, Chapter V, Subchapter C - Electronic Product Radiation Control.

Microwave oven manufacturers are exempt from product reports ( 1002.10) except the first product report. Please also see 21 CFR 1002.1, Table 1 Record and Reporting Requirements by Product, Footnote 8

The modern world is full of devices that, either directly or indirectly, act as sources of non-ionizing radiation (NIR). These sources produce NIR in the electromagnetic spectrum of wavelengths/frequencies ranging from 100 nm to static fields. Many NIR sources are present on the UC Berkeley campus, either in research applications or in ancillary equipment.

In general, NIR tends to be less hazardous to humans than ionizing radiation (ionizing radiation has a wavelength of less than 100 nm or a photon energy greater than 12.4 electron Volts). However, depending on the wavelength/frequency and the irradiance (or power density) value, NIR sources may present a human health hazard. This manual is intended to provide guidance in maintaining a safe NIR work environment on the campus.

3a8082e126