Chapter 22 – The Nature of Light Section 2 – The Electromagnetic Spectrum pp. 636-643.

Chapter 22 – The Nature Chapter 22 – The Nature of Lightof Light

Section 2 – The Section 2 – The Electromagnetic SpectrumElectromagnetic Spectrum

pp. 636-643pp. 636-643

TERMS TO LEARNTERMS TO LEARN

Electromagnetic spectrum – Electromagnetic spectrum – the entire range of EM wavesthe entire range of EM waves

UV light – UV light – EM waves that are EM waves that are between visible light and x-between visible light and x-rays on the EM spectrum.rays on the EM spectrum.

CHARACTERISTICS OF EM CHARACTERISTICS OF EM WAVESWAVES

All EM waves travel at the same All EM waves travel at the same speed in a vacuum (speed in a vacuum (300,000,000 300,000,000 m /sm /s))

Categories of waves in the EM Categories of waves in the EM spectrum include:spectrum include:

1.1. Radio wavesRadio waves

2.2. MicrowavesMicrowaves

3.3. Visible lightVisible light

EM SPECTRUMEM SPECTRUM

RADIO WAVESRADIO WAVES

Have some of Have some of the the longest longest wavelengths and wavelengths and lowest lowest frequencies of all frequencies of all the EM wavesthe EM waves

Are low energy Are low energy waveswaves

AM VS. FM WAVESAM VS. FM WAVES

Amplitude Amplitude Modulation (A.M.)Modulation (A.M.)

Frequency Frequency modulation (F.M.)modulation (F.M.)

Can travel farther Can travel farther than FMthan FM

More information More information can be encoded can be encoded than AMthan AM

Can reflect off the Can reflect off the ionosphereionosphere

Passes through the Passes through the ionosphereionosphere

Have longer Have longer wavelengths than wavelengths than AMAM

Have shorter Have shorter wavelengths than wavelengths than AMAM

TV AND RADIO WAVESTV AND RADIO WAVES

TV AND RADIO WAVESTV AND RADIO WAVES

TV uses radio waves TV uses radio waves that have that have shorter wavelength and higher shorter wavelength and higher frequency than those used by radio frequency than those used by radio stationsstations..

Most TV stations are broadcast using Most TV stations are broadcast using A.M. and F.M. A.M. and F.M.

F.M. waves carry sound; A.M. waves F.M. waves carry sound; A.M. waves carry picturescarry pictures

MICROWAVESMICROWAVES

Have shorter Have shorter wavelength and wavelength and higher frequency higher frequency than radio waves.than radio waves.

Carry more energy Carry more energy than radio waves.than radio waves.

Microwaves are Microwaves are also used in radar also used in radar ((radio detection radio detection and rangingand ranging).).

INFRARED WAVESINFRARED WAVES

Have shorter Have shorter wavelengths and wavelengths and higher frequency higher frequency than microwaves.than microwaves.

Can carry more Can carry more energy than energy than microwaves and microwaves and radio wavesradio waves

INFRARED WAVESINFRARED WAVES

The Sun is a The Sun is a source of IR source of IR waves.waves.

Stars, planets, Stars, planets, buildings, buildings, humans and humans and trees also emit trees also emit IR waves.IR waves.

IR WAVESIR WAVES

The amount of IR The amount of IR radiation emitted by an radiation emitted by an object depends on object depends on the the temperature of the temperature of the objectobject. Warmer objects . Warmer objects give off more IR give off more IR radiation than cooler radiation than cooler ones.ones.

Your eyes cannot see IR Your eyes cannot see IR radiation but there are radiation but there are devices that can detect devices that can detect it (i.e. it (i.e. night vision night vision gogglesgoggles))

VISIBLE LIGHTVISIBLE LIGHT

VISIBLE LIGHTVISIBLE LIGHT

Humans can see it.Humans can see it. The spectrum consists of The spectrum consists of ROYGBIVROYGBIV.. RRed, ed, OOrange, range, YYellow, ellow, GGreen, reen, BBlue, lue,

IIndigo, ndigo, VViolet.iolet. White light is White light is all of the colors of all of the colors of

visible light combinedvisible light combined..

VISIBLE LIGHTVISIBLE LIGHT

Red light has the Red light has the longest longest wavelength of all the visible wavelength of all the visible light. It carries the least amount light. It carries the least amount of energy.of energy.

Violet light has the Violet light has the shortest shortest wavelength of visible light. It wavelength of visible light. It carries the most energy.carries the most energy.

UV LIGHTUV LIGHT

Also produced by Also produced by the Sun.the Sun.

Has shorter Has shorter wavelength and wavelength and higher frequency higher frequency than visible light.than visible light.

Carries more Carries more energy than visible energy than visible lightlight..

EFFECTS OF UV WAVESEFFECTS OF UV WAVES

Positive EffectsPositive Effects Negative EffectsNegative Effects

Used to kill bacteria Used to kill bacteria in foodin food

Overexposure can Overexposure can cause sunburn, skin cause sunburn, skin cancer, eye damagecancer, eye damage

Causes skin cells to Causes skin cells to produce Vitamin Dproduce Vitamin D

Overexposure can Overexposure can cause wrinkles and cause wrinkles and premature aging of premature aging of the skinthe skin

X-RAYSX-RAYS

Have the shortest Have the shortest wavelengths and wavelengths and highest frequency of highest frequency of all EM wavesall EM waves..

X-rays carry a lot of X-rays carry a lot of energy and can energy and can penetrate many penetrate many materials.materials.

Too much exposure to Too much exposure to x—rays can damage x—rays can damage or kill living cellsor kill living cells

GAMMA RAYSGAMMA RAYS

Carry large amounts of energy and can Carry large amounts of energy and can penetrate materials very easily.penetrate materials very easily.

Every day you are exposed to small Every day you are exposed to small amounts of gamma rays that do not harm amounts of gamma rays that do not harm you.you.

Radiologists focus these on tumors to kill Radiologists focus these on tumors to kill cancer cells.cancer cells.

A negative effect of gamma radiation is A negative effect of gamma radiation is that they kill healthy cells.that they kill healthy cells.