The Electromagnetic Spectrum 1MAP TAP 2003-2004

The Electromagnetic Spectrum

Wavelength/frequency/energy

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Teacher Page

• Content: Physical Science—The Electromagnetic Spectrum

• Grade Level: High School• Creator: Dorothy Walk• Curriculum Objectives: SC 1; Intro

Phys/Chem IV.A (waves)

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What is it?

• The electromagnetic spectrum is the complete spectrum or continuum of light including radio waves, infrared, visible light, ultraviolet light, X-rays and gamma rays

• An electromagnetic wave consists of electric and magnetic fields which vibrates thus making waves.

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Waves

• Properties of waves include speed, frequency and wavelength

• Speed (s), frequency (f) and wavelength (l) are related in the formula l x f = s

• All light travels at a speed of 3 s 108 m/s in a vacuum

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Wavelength, Frequency and Energy

• Since all light travels at the same speed, wavelength and frequency have an indirect relationship.

• Light with a short wavelength will have a high frequency and light with a long wavelength will have a low frequency.

• Light with short wavelengths has high energy and long wavelength has low energy

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Radio waves

• Low energy waves with long wavelengths• Includes FM, AM, radar and TV waves• Wavelengths of 10-1m and longer• Low frequency • Used in many devices such as remote control

items, cell phones, wireless devices, etc.

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Microwaves

• Longer than radio, shorter than light and infrared

• Wavelength 1 x 10 - 4 m to 1 x 10-1 m

• First used in radar, now used in communication, medicine and consumer use (microwave ovens)

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Infrared waves

• Invisible electromagnetic waves that are detected as heat

• Can be detected with special devices such as night goggles

• Used in heat lamps• Higher energy than microwaves

but lower than visible light

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Visible Light

• The portion of the electromagnetic spectrum that human eyes can detect

• ROY G BIV (red, orange, yellow, green, blue, indigo, violet)

• Red is the lowest frequency and violet is the highest frequency

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Ultraviolet waves

• Higher energy than light waves• Can cause skin cancer and blindness in

humans• Used in tanning beds and sterilizing

equipment

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X-Rays

• High energy waves• First discovered by

Roentgen • Used in medicine,

industry and astronomy• Can cause cancer

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Gamma rays

• Highest energy• Blocked from Earth’s surface

by atmosphere

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Time to think…..

• 1. What is the relationship between frequency and wavelength?

• 2. What is meant by ‘spectrum’?

• 3. What does ROY G BIV mean?

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Now, let’s really think

• 4. Can you actually see x-rays?– Support your answer.

• 5. Which color is more energetic, red or yellow?

• 6. Which type of wave travels faster, gamma or radio?

• 7. Why are microwaves more dangerous than radio waves?

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Think about it….

• You have just been involved in a traffic incident that leaves you stranded on the side of the road. Which part of the electromagnetic spectrum would be of the most use to you and why?

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Answers• 1. Frequency and wavelength are properties of waves and since

speed is constant for em waves, as frequency increases, wavelength decreases.

• 2. Spectrum is a continuum of all electromagnetic waves• 3, ROY G BIV is the difference colors of the visible light in order of

longest wavelength to shortest wavelength.• 4. X-rays can not be seen, only the waves in the visible light portion

are visible.• 5. Yellow is higher energy than red because it has a shorter

wavelength and higher frequency.• 6. Both travel at the same speed, 300,000 km/s (all em waves travel

at the same speed)• 7. Microwaves have a higher frequency than radio and carry more

energy.