Electromagnetic Waves

By Janey Cavallaro

Electromagnetic Waves vs Mechanical Waves

Electromagnetic waves, or EM waves, can travel through a vacuum, although mechanical waves cannot. In order to travel, mechanical waves require a medium. Mechanical waves are caused by disturbances in matter, such as a solid, liquid, or gas. An example of this would be a sound wave. Sounds create a disturbance and can only travel through matter. In space, there is no sound because space is a vacuum. Electromagnetic waves are caused by a vibrating electric charge. EM waves create disturbances in the electric field and the magnetic field because the two are connected. Electromagnetic waves can be produced on the Sun, however mechanical waves are created on Earth.
Electromagnetic Radiation

Examples of the EM Spectrum

Radio- Radio waves are transmitted by radio stations. They are then picked up by radios in your house and car. Radio waves often have low frequency. The transmitted waves use diffraction to bend around things such as hills to reach radios. Since they have a low frequency, radio waves have a long wavelength. Radio waves are transmitted by stations, but they can also be transmitted by stars and gases in space. Low frequency radio waves are reflected off the Ionosphere, the upper most layer of the Earth that is electrically charged. This is what allows radio waves to reach their destination, even if it is not in their line of sight.


Microwave- Microwave radiation has a low frequency and a long wavelength. Most waves are absorbed by water, so when you heat up food in the microwave, the water in the food absorbs the radiation and causes the food to heat up. Microwave radiation is also used for cell phone signals. Some radiation can pass through the Earth's atmosphere and are used to transmit information to Earth's orbiting satellites.


Infrared- Infrared radiation is absorbed by skin. Humans recognize it as heat. These waves are also used in grills, heaters, and toasters. One example of a infrared radiation is night vision goggles. They pick up on the infrared radiation that our bodies give off and that is what allows you to be able to see. One final example is tv remotes. The frequency is higher than microwaves and radios, but still fairly low. As the frequency increases, the wavelength gets shorter. Another way infrared radiation helps us is it allows us to see the dust in space between stars.

EM Spectrum Continued

Visible Light- Our eyes are able to detect visible light. Stars, fireflies, and light bulbs are all examples of visible light. In visible light, the frequency starts to get higher and the wavelength gets shorter. There is a visible light spectrum that allows us to see colors. Red wavelengths tend to be longer, and violet wavelengths are shorter.


Ultraviolet Rays- Ultraviolet rays are found in sunlight. They are what make people tanner or in my case, sunburned. Your skin turns darker because your body is trying to reduce the amount of ultraviolet rays in your tissue. Ultraviolet radiation can often cause cancer. Ultraviolet rays are used in tanning beds and florescent lights. This type of radiation has high frequency and short wavelength.


X-Rays and Gamma Rays- Neither x-rays nor gamma rays can be seen or felt. X-rays are used to see if people have damaged bones. They can see through skin and soft tissue, but not bones and metal. Dentist use x-rays to check patients teeth. X-rays are also used at airports for security to check passengers bags. X-rays have high frequency and short wavelength. Gamma rays ave very high frequency and very short wavelength. Gamma radiation can pass through skin and tissue. They are often absorbed by cells. Gamma radiation is used to kill cancer cells, sterilize surgical tools, and kill harmful bacteria in food.

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