Light: Electromagnetic Radiation

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
25 cm (start)
25 cm (10 minutes
25 cm (start)
25 cm (10
minutes after)
Electromagnetic Radiation
 Transverse waves produced by electrically charged
 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
 Radiation carries energy and momentum
 Light is composed of tiny particles called
 Photons with the highest energy
correspond to light with the highest
 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
 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
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
 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