Light: Electromagnetic Radiation
Important Vocabulary
 Electromagnetic radiation
 X ray
 Photon
 Gamma ray
 Radio wave
 Microwave
 Infrared radiation
 Visible radiation
 Ultraviolet radiation
 Fold each piece of construction paper to form a sleeve.
 Insert a thermometer into each sleeve.
 Place it 25 cm from a light source, record temperature
 Wait 10 minutes, record temperature of each sleeve
again
Color
25 cm (start)
25 cm (10 minutes
after)
Color
Black
Yellow
Orange
Blue
25 cm (start)
25 cm (10
minutes after)
Electromagnetic Radiation
 Transverse waves produced by electrically charged
particles
 They radiate from particles
 The transfer of energy by electromagnetic waves is
called radiation
 They DO NOT need a medium to transfer energy
 Travel faster than sound or water waves
Electromagnetic Radiation
 Travel at the same speed in a vacuum, but
frequencies and wavelengths differ
 Shorter the wavelength the __________ the
frequency
 Radiation carries energy and momentum
 Light is composed of tiny particles called
photons
 Photons with the highest energy
correspond to light with the highest
frequency
 High energy photons can damage matter
Radio Waves
 When you tune a radio to a station, you are
adjusting to respond to radio waves of a
certain frequency
 Long wavelengths and low frequencies
 High / Low photon energy
 Used in television, cellular telephones and
cordless telephones
Radio Waves
 Radio waves with the highest frequency and
energy are called microwaves
 Used in communications and speedy cooking
 Microwaves transfer energy to the water molecules
that are inside food, causing them to vibrate and
move faster
 The result is the kinetic energy and temperature of
the water molecules increase
Infrared Radiation
 Infrared Radiation has a wavelength slightly longer
than visible light
 Think of a nice sunny day, what happens to your
skin? What happens when the clouds cover the
sun?
 Warm objects give off more infrared radiation than
cool objects
 Measurements of the body’s emission of infrared
radiation help doctors make medical diagnosis
Visible Radiation – light
The only part of the electromagnetic
spectrum that you can see
Light can also cause chemical reactions to
occur such a as:

Can stimulate decomposition reactions of
materials
Ultraviolet Radiation
 Why do you wear sunglasses or sunscreen in strong sunlight?
 Ultraviolet radiation has a higher frequency than visible light
 Photons are more energetic and have greater power than
photons of visible light
 Exposure to UV rays produce vitamin D, kill bacteria, and
sterilize surgical instruments
 Overexposure can lead to damaged skin, cancer
 Ozone protects us from UV rays
Ozone
 Earth’s natural filter
 Blocks most of the sun’s UV rays
 It is a form of oxygen where oxygen atoms
cobmine to make each ozone molecule
 Reduction in the ozone = an increase in UV rays
 Chemicals break down ozone
X Rays
Gamma Rays
Homework p. 535 #1-3