Chapter 4.3

Light and the Electromagnetic Spectrum

Waves are everywhere!

• We are surrounded….…by waves of radiation.

• Some we can see, such as visible light

• Some we cannot see such as radio waves

• As light leaves the sun, it spreads out

• Radiant energy is energy that travels in the form of radiation

• There are many forms of radiation

Electromagnetic Radiation

• In a light wave, electrical and magneticfields vibrate

• Therefore, we call light “electromagnetic” radiation

• There is a spectrum called the electromagnetic spectrum:– It includes visible light and other types of

invisible radiant energy

Electromagnetic Radiation

• All forms of electromagnetic radiation travel as waves

• They range from long to short wavelengths(and high to low frequency)

1. Radio Waves

• Radio waves have the longest wavelength

• They are the lowest energy and lowest frequency waves

Uses of Radio Waves

• Radio and tv broadcasting

• Cellular phones

• Testing for illness (MRI – magnetic resonance imaging)

• Radar

• Microwaves

2. Microwaves

• A type of radio wave

• Microwaves have the shortest wavelength and the highestfrequency of radiowaves

Microwave ovens use a specific wavelength of microwave

Uses of Microwaves

• Uses:

– Microwave ovens

– Telecommunications (satellites)

– Radar (tracking objects, weather forecasting)

A microwave communication tower in Munich, Germany →

3. Infrared Waves• These waves have a longer wavelength than

visible light (lower frequency).

• Infrared waves are around us everyday!

• Also known as “heat radiation”

– Warm objects emit more infrared radiation than cooler objects

– Used with night goggles and in airports to see if passengers have a fever!

Uses of Infrared Waves

• Uses:– Heat lamps (keep

food warm)– Remote controls– Computers (to

read CD-ROMs)– Used with

satellites to detect forest fires

4. Visible Light

• Visible light is electromagnetic radiation at a wavelength and frequency that we can detect with our eyes.

• It lies around the middle of the spectrum…

5. Ultraviolet Waves

• Just beyond the end of the visible region of the spectrum are UV waves

• Have a shorter wavelength and higher frequency than visible light

5. Ultraviolet Waves

• When UV light hits your skin, it allows you to make vitamin D (important for healthy bones and teeth)

• Too much UV exposurecan cause damage

Uses of UV Waves

• Flourescent materials such as powder for fingerprints (absorb UV and emitvisible light)

• Destroy bacteria in food and water

• Insect vision (butterflies)

6. X Rays

• Much higher energy(frequency) and shorter wavelengththan UV waves

• Often used in medical field to take X ray photographs of bones and teeth

Uses of X Rays

• Images of organs, bones and teeth

• Airport security (x-ray screening of baggage)

• Inspect for cracks in engines of jets

7. Gamma Rays

• The highest energywaves in the spectrum

• Shortest wavelength and highest frequency

• Produced from nuclear reactions

• Used in specific burst to kill cancer cells.