Electromagnetic Waves

By Grace Johnson

Summary

When there is a disturbance in a field of electric and magnetic waves, electromagnetic waves are created. These waves contain high points and low points, or crests and troughs. At the crest, the highest point, the electric field is highest and the electric field is lowest at the trough, the lowest point. There are significant differences between electromagnetic and mechanical waves. For example, electromagnetic waves can pass through a vacuum, but mechanical waves require a medium. Electromagnetic waves also contain an electric and magnetic component that mechanical waves do not possess.

The Electromagnetic Spectrum

The electromagnetic spectrum includes all of the wavelengths of electromagnetic radiation. Visible light is the only type of electromagnetic wave that the human eyes can see.

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Gamma Rays

Gamma rays contain the shortest wavelengths, the highest frequency in the spectrum, and are about the size of an atomic nucleus. They are formed by the hottest and most high energy objects such as neutron stars and pulsars, supernova explosions, and areas surrounding black holes. Gamma rays are so small that they cannot be reflected or captured by mirrors. Scientists use gamma rays to find elements on other planets. The system used to detect these elements emits gamma rays. When the elements come in contact with the rays, they release signatures of energy used to identify the element. Gamma rays are also used by doctors to create ray images of the body.


Wavelength < 1 x 10^-11 m

Frequency > 3 x 10^19 Hz.

Energy > 2 x 10^-14 J

X-Rays

X-rays were discovered in 1895 by a German scientist named Wilhelm Conrad. These waves are shot through the body to create images of the bones. There is an x-ray sensitive film placed behind the body and x-rays pass through. The bones absorb most of the waves and the rest pass through to hit the film to create images of shadows. X-rays are not always used in the medical field. They are also used in telescopes to take pictures of supernovas.


Wavelength = 1 x 10^-11 - 1 x 10^-8 m

Frequency = 3 x 10^16 - 3 x 10^19 Hz.

Energy = 2 x 10^-17 - 2 x 10^-14 J

Ultra Violet

Ultraviolet waves cannot be seen by the human eye, but are visible to some insects such as bumblebees. The sun is a source of ultraviolet radiation. These waves are classified as UV-A, UV-B, and UV-C rays. UV-B is the type of ray that causes sunburn, but 95% of UV-B rays are absorbed by our atmosphere. Ultraviolet light is used to capture images of different galaxies. It was also used to create a map of the moon that is used to view craters.


Wavelength = 1 x 10^-8 - 4 x 10^-7 m

Frequency = 7.5 x 10^14 - 3 x 10^16 Hz.

Energy = 5 x 10^-19 - 2 x 10^-17 J

Visible Light

Visible light is the portion of the spectrum that is visible to humans. When the spectrum of visible light passes through a prism, the wavelengths separate into the colors of the rainbow known as ROYGBIV. At one side of the spectrum, beginning with red, the wavelengths are long and the frequencies are low. As you pass through the spectrum to violet, the wavelengths get shorter and the frequencies get higher. White is seen when all colors of the spectrum are combined and black is seen where there is an absence of light. Visible light is most obviously used by humans to perceive the world around them. It is used in photography, video production, lighthouses, and many others. Scientists can use visible light to determine the temperature of stars.


Wavelength = 4 x 10^-7 - 7 x 10^-7 m

Frequency = 4 x 10^14 - 7.5 x 10^14 Hz.

Energy = 3 x 10^-19 - 5 x 10^-19 J

Infrared

Infrared was first discovered in 1800 by William Herschel. He was conducting an experiment to measure the temperatures of the colors in the visible light spectrum when he noticed that a thermometer with no visible light hitting it had a higher temperature than the other thermometers. Infrared waves are typically used with heat, but have other purposes as well. Infrared heat lamps use infrared waves to keep food warm or heat bathrooms. These waves are used in television remotes, too. Thermal imaging is another example of infrared. These images allow us to see the temperatures of objects. Infrared is also used to see objects in the universe that are too cool and faint to be seen.


Wavelength = 7 x 10^-7 - 1 x 10^-3 m

Frequency = 3 x 10^11 - 4 x 10^14 Hz.

Energy = 2 x 10^-22 - 3 x 10^-19 J

Microwaves

Microwaves are used heating up food, weather forecasting, and GPS. The waves are sent by satellites that transmit information back and forth from the GPS. In a microwave, the waves force the water and fat molecules in the food to rotate, causing the food to cook. Microwaves are also used to transmit signals used for phone calls. When these waves are used to create Doppler-radar images, a satellite measures changes in the energy of the microwave pulses. The satellite can then tell the speed and direction of wind and can also monitor the conditions of hurricanes.


Wavelength = 1 x 10^-3 - 1 x 10^-1 m

Frequency = 3 x 10^9 - 3 x 10^11 Hz.

Energy = 2 x 10^-24- 2 x 10-^22 J

Radio Waves

Radio waves were first discovered by Heinrich Hertz in an experiment he conducted in the late 1880’s. These waves can be as large as a football to bigger than the earth. When you tune into a radio station, you are just tuning into a certain wavelength or frequency. The radio then receives the radio waves and turns them into mechanical vibrations in your speaker that you can hear. Besides being used in radios, radio waves are also used in telescopes. These telescopes study planets, comets, clouds of gas and dust, stars, and galaxies.


Wavelength > 1 x 10^-1 m

Frequency < 3 x 10^9 Hz.

Energy < 2 x 10^-24 J