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

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.

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

EM SPECTRUM

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

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

TV AND RADIO WAVES

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

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).

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

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

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)

VISIBLE LIGHT

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.

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.

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

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

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

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.