The The Electromagnetic Electromagnetic

SpectrumSpectrum

The waves of the The waves of the spectrumspectrum Herschel used a prism to separate the Herschel used a prism to separate the

wavelengths present in sunlight.wavelengths present in sunlight. The colors he produced were red, orange, The colors he produced were red, orange,

yellow, green, blue, and violet.yellow, green, blue, and violet. Noticed the different color lights had Noticed the different color lights had

different temperatures, so must have different temperatures, so must have different energies.different energies.

The entire range of frequencies is called the The entire range of frequencies is called the electromagnetic spectrum.electromagnetic spectrum.

Includes radio waves, microwaves, infrared Includes radio waves, microwaves, infrared waves, visible light, ultraviolet rays, X-rays, waves, visible light, ultraviolet rays, X-rays, and gamma raysand gamma rays

The electromagnetic The electromagnetic spectrumspectrum

Radio wavesRadio waves Longest wavelengths, lowest frequencies.Longest wavelengths, lowest frequencies. Wavelengths can be the size of buildings.Wavelengths can be the size of buildings. Used in radio and television, microwave ovens, Used in radio and television, microwave ovens,

and radarand radar

RadioRadio

Voices that have been changed into electronic Voices that have been changed into electronic signals are coded onto radio waves and signals are coded onto radio waves and broadcast.broadcast.

Use amplitude modulation (AM) and frequency Use amplitude modulation (AM) and frequency modulation(FM).modulation(FM).

Amplitude modulation uses a constant frequency Amplitude modulation uses a constant frequency and changes the amplitude of the wave.and changes the amplitude of the wave.

Frequency modulation uses a constant Frequency modulation uses a constant amplitude and changes the frequency.amplitude and changes the frequency.

The radio at your house or in your car decodes The radio at your house or in your car decodes these signals and changes them into sound these signals and changes them into sound waves you can hear.waves you can hear.

TelevisionTelevision

These radio waves carry information for These radio waves carry information for pictures and sound.pictures and sound.

Your TV picks up the signal and turns it back Your TV picks up the signal and turns it back into sound and pictures.into sound and pictures.

TV reception can be affected by weather.TV reception can be affected by weather. Satellite TV gets its signals from TV Satellite TV gets its signals from TV

broadcasts that are sent to satellites in broadcasts that are sent to satellites in space.space.

Cable TV receives the signals for people that Cable TV receives the signals for people that do not have a satellite dish and sends them do not have a satellite dish and sends them to their home.to their home.

MicrowavesMicrowaves Shortest radio wavesShortest radio waves Used in microwave ovens and cell phones.Used in microwave ovens and cell phones. Cell phones work the same way radio waves Cell phones work the same way radio waves

do.do. Microwave ovens use the energy in the wave Microwave ovens use the energy in the wave

to heat up food particles.to heat up food particles. Microwaves only penetrate the surface of Microwaves only penetrate the surface of

foods which is why you have to let the food foods which is why you have to let the food sit so the food can be heated by conduction.sit so the food can be heated by conduction.

Infrared wavesInfrared waves Shorter wavelengths than radio wavesShorter wavelengths than radio waves Used as a source of heat to discover areas of Used as a source of heat to discover areas of

heat differences.heat differences. Infrared lamps are used to keep food warm at Infrared lamps are used to keep food warm at

restaurants.restaurants. You can’t see infrared radiation, but you can You can’t see infrared radiation, but you can

feel it has heat.feel it has heat. Can be used to find people trapped in Can be used to find people trapped in

buildings, homes, or other structures after a buildings, homes, or other structures after a natural disaster.natural disaster.

Visible LightVisible Light The only part of the electromagnetic The only part of the electromagnetic

spectrum you can see.spectrum you can see. Each wavelength corresponds to a different Each wavelength corresponds to a different

frequency (energy) and a different color.frequency (energy) and a different color. Red light has the longest wavelength and Red light has the longest wavelength and

lowest frequency (energy).lowest frequency (energy). Violet light has the shortest wavelength Violet light has the shortest wavelength

and the highest frequency (energy).and the highest frequency (energy).

Ultraviolet radiationUltraviolet radiation Has higher frequency than violet light.Has higher frequency than violet light. Comes from the sun.Comes from the sun. Used in health, medicine, and agriculture.Used in health, medicine, and agriculture. Helps our skin produce vitamin D which helps ourHelps our skin produce vitamin D which helps our

bodies to absorb calcium for our bones and teeth.bodies to absorb calcium for our bones and teeth. Can cause sunburn, skin cancer, or damage to Can cause sunburn, skin cancer, or damage to

eyes.eyes.

X-raysX-rays Very short wavelengths.Very short wavelengths. Used in medicine, industry, and Used in medicine, industry, and

transportation to take pictures of the insides transportation to take pictures of the insides of solid objects.of solid objects.

Teeth and bones absorb X-rays and appear Teeth and bones absorb X-rays and appear white in X-ray photographs. Softer tissue white in X-ray photographs. Softer tissue appears dark.appears dark.

Gamma raysGamma rays Shortest wavelengths in the spectrum.Shortest wavelengths in the spectrum. Have the most energy and penetrating Have the most energy and penetrating

ability of all the waves of the spectrum.ability of all the waves of the spectrum. Used to kill cancer cells and to take Used to kill cancer cells and to take

pictures of the brain.pictures of the brain. Used in radiation therapy to kill cancer Used in radiation therapy to kill cancer

cells while not damaging healthy cells.cells while not damaging healthy cells. Overexposure can be deadly.Overexposure can be deadly.

microwavesmicrowaves This is a radar image This is a radar image

acquired from the acquired from the Space Shuttle. It also Space Shuttle. It also used a wavelength in used a wavelength in the L-band of the the L-band of the microwave spectrum. microwave spectrum. Here we see a Here we see a computer enhanced computer enhanced radar image of some radar image of some mountains on the edge mountains on the edge of Salt Lake City, of Salt Lake City, Utah. Utah.

infraredinfrared

This image (courtesy of This image (courtesy of SE-IR Corporation, SE-IR Corporation, Goleta, CA) shows a cat Goleta, CA) shows a cat in the infrared. The in the infrared. The orange areas are the orange areas are the warmest and the white-warmest and the white-blue areas are the blue areas are the coldest. This image gives coldest. This image gives us a different view of a us a different view of a familiar animal as well as familiar animal as well as information that we could information that we could not get from a visible not get from a visible light picture. light picture.

Visible lightVisible light

When white light When white light shines through a shines through a prism or through prism or through water vapor like water vapor like this rainbow, the this rainbow, the white light is white light is broken apart into broken apart into the colors of the the colors of the visible light visible light spectrum. spectrum.

ultravioletultraviolet Our Sun emits light at all Our Sun emits light at all

the different wavelengths in the different wavelengths in electromagnetic spectrum, electromagnetic spectrum, but it is ultraviolet waves but it is ultraviolet waves that are responsible for that are responsible for causing our sunburns. To causing our sunburns. To the left is an image of the the left is an image of the Sun taken at an Extreme Sun taken at an Extreme Ultraviolet wavelength - Ultraviolet wavelength - 171 Angstroms to be exact. 171 Angstroms to be exact. This image was taken by a This image was taken by a satellite named SOHO and satellite named SOHO and it shows what the Sun it shows what the Sun looked like on April 24, looked like on April 24, 2000. 2000.

Skin cancer

X-raysX-rays

When X-ray light When X-ray light shines on us, it goes shines on us, it goes through our skin, but through our skin, but allows shadows of allows shadows of our bones to be our bones to be projected onto and projected onto and captured by film. This captured by film. This is an X-ray photo of a is an X-ray photo of a one year old girl. Can one year old girl. Can you see the shadow you see the shadow of what she of what she swallowed?swallowed?

Gamma raysGamma rays If you could see If you could see

gamma-rays, the gamma-rays, the night sky would look night sky would look strange and strange and unfamiliar. The unfamiliar. The gamma-ray moon just gamma-ray moon just looks like a round looks like a round blob - lunar features blob - lunar features are not visible. In are not visible. In high-energy gamma high-energy gamma rays, the Moon is rays, the Moon is actually brighter actually brighter than the quiet Sun. than the quiet Sun. This image was taken This image was taken by EGRET. by EGRET.