1. Chapter 22 – The Nature of Light
Section 2 – The Electromagnetic Spectrum pp

2. TERMS TO LEARN Electromagnetic spectrum – the entire range of EM waves
UV light – EM waves that are between visible light and x-rays on the EM spectrum.

3. CHARACTERISTICS OF EM WAVES
All EM waves travel at the same speed in a vacuum (300,000,000 m /s)
Categories of waves in the EM spectrum include:
Radio waves
Microwaves
Visible light

4. EM SPECTRUM

5. RADIO WAVES
Have some of the longest wavelengths and lowest frequencies of all the EM waves
Are low energy waves

6. AM VS. FM WAVES Amplitude Modulation (A.M.)
Frequency modulation (F.M.)
Can travel farther than FM
More information can be encoded than AM
Can reflect off the ionosphere
Passes through the ionosphere
Have longer wavelengths than AM
Have shorter wavelengths than AM

7. TV AND RADIO WAVES

8. TV AND RADIO WAVES
TV uses radio waves that have shorter wavelength and higher frequency than those used by radio stations.
Most TV stations are broadcast using A.M. and F.M.
F.M. waves carry sound; A.M. waves carry pictures

9. MICROWAVES
Have shorter wavelength and higher frequency than radio waves.
Carry more energy than radio waves.
Microwaves are also used in radar (radio detection and ranging).

10. INFRARED WAVES
Have shorter wavelengths and higher frequency than microwaves.
Can carry more energy than microwaves and radio waves

11. INFRARED WAVES The Sun is a source of IR waves.
Stars, planets, buildings, humans and trees also emit IR waves.

12. IR WAVES
The amount of IR radiation emitted by an object depends on the temperature of the object. Warmer objects give off more IR radiation than cooler ones.
Your eyes cannot see IR radiation but there are devices that can detect it (i.e. night vision goggles)

13. VISIBLE LIGHT

14. VISIBLE LIGHT Humans can see it. The spectrum consists of ROYGBIV.
Red, Orange, Yellow, Green, Blue, Indigo, Violet.
White light is all of the colors of visible light combined.

15. VISIBLE LIGHT
Red light has the longest wavelength of all the visible light. It carries the least amount of energy.
Violet light has the shortest wavelength of visible light. It carries the most energy.

16. UV LIGHT Also produced by the Sun.
Has shorter wavelength and higher frequency than visible light.
Carries more energy than visible light.

17. EFFECTS OF UV WAVES Positive Effects Negative Effects
Used to kill bacteria in food
Overexposure can cause sunburn, skin cancer, eye damage
Causes skin cells to produce Vitamin D
Overexposure can cause wrinkles and premature aging of the skin

18. X-RAYS
Have the shortest wavelengths and highest frequency of all EM waves.
X-rays carry a lot of energy and can penetrate many materials.
Too much exposure to x—rays can damage or kill living cells

19. GAMMA RAYS
Carry large amounts of energy and can penetrate materials very easily.
Every day you are exposed to small amounts of gamma rays that do not harm you.
Radiologists focus these on tumors to kill cancer cells.
A negative effect of gamma radiation is that they kill healthy cells.