3. What is an Electromagnetic Wave
Wave that transfers energy without a medium
Vibration of electric and magnetic fields that
move through space at the speed of light
Created by moving an electric charge
Called electromagnetic radiation
71
4. Speed
Speed in a vacuum 300,000 kilometers per second
From sun to Earth?
8 minutes
Light slows down when it enters a medium
72
5. Models
Wave Model
Light travels in many directions at once
Polarizing filters block all but light in one direction
72
6. Models
Particle Model
Light is a tiny particle moving through space
Called photon
Light bump up electrons in atoms
Called photoelectric effect
73
11. Infrared Rays
Heat waves that you feel but can not see
Heat Lamps
Infrared Cameras
Warmer objects give off more waves than cold
Satellites
Locate people
77
12. Visible Light
Small part of electromagnetic spectrum
Longest waves = Red
Shortest waves = Violet
Visible light is a mixture of all wavelengths – White
When bending in a new medium red bends least
The color you see is what is reflected
(rest of light is absorbed)
78
13. Ultraviolet Rays
Much shorter waves than visible light (more energy)
Very dangerous
Cause damage
Cancer cells
Eye damage
Kill bacteria (used in hospitals/labs)
Sunscreen and sunglasses used to black these rays
Ozone layer blocks many of these rays
78
14. X-Rays
High energy
Penetrates most tissues
Blocked only by very dense structures
Bone / Lead
Used in medicine and structural analysis to look for
damage
79
15. Gamma Rays
Extremely high energy
Used in medicine to kill cancer cells
Can not penetrate Earth atmosphere
Telescopes put into space to detect
Discovery of astronomical events
Stars, black holes, galaxies…
80