1. Electromagnetic Waves
Chap. 18

2. What are Electromagnetic Waves?
Electromagnetic waves are produced when an electric charge vibrates or accelerates.

3. How they Travel
They can travel through empty space as well as through matter!
The transfer of energy by electromagnetic waves traveling through matter or across space is called electromagnetic radiation.

4. Speed of Electromagnetic Waves
Yes, electromagnetic waves travel at a constant speed through a vacuum, c.
The speed of light in a vacuum is 300,000,000 m/s.

5. Michelson’s Experiment
See pg. 534 in your text.

6. Measure the speed
The equation here is the same as the one for mechanical waves.
Speed = wavelength x frequency

7. Wave or Particle?
What is light?
There are two theories.

8. Evidence for a Wave

9. Another view or this

10. Light is a Particle
Electrons are emitted from a metal plate when blue or ultraviolet light strikes it.

11. Dual Nature of Light

12. Light Intensity
Intensity of light decreases as photons travel farther from the source. Because the total energy does not change, the wave’s intensity decreases.

13. The Electromagnetic Spectrum

14. Types of Electromagnetic Waves
Radio waves: Used in radio and television technologies, as well as in microwave ovens and radar.
Infrared: Used as a source of heat and to discover areas of heat differences.
Visible Light: The part of the spectrum that is visible to humans.

15. Ultraviolet Rays: Have applications in health and medicine, and in agriculture.
X-Rays: Used in medicine, industry, and transportation to make pictures of the inside of solid objects.
Gamma Rays: Used in the medical field to kill cancer cells and make pictures of the brain, and in industrial situations as an inspection tool.

16. Behavior of Light
How light behaves when it strikes an object depends on the material the object is made of.
Materials can be:
Transparent
Translucent
Opaque

17. Transparent? Translucent? Opaque?

18. Transparent? Translucent? Opaque?

19. Transparent? Translucent? Opaque?

20. Interactions of Light
When light strikes a new medium, it can be reflected, absorbed, or transmitted.
When it is transmitted, it can be refracted, polarized, or scattered.

21. Reflection, Absorption, Transmission
Regular reflection: when parallel light waves strike a surface and reflect all in the same direction.
Ex:

22. Diffuse Reflection
When parallel light waves strike a rough, uneven surface.

23. Refraction
A light wave can refract, or bend, when it passes at an angle from one medium into another.

24. Refraction Again

25. Refraction, one last time
Reflection and Refraction

26. Refraction, one last time
index of refraction
Diamond 2.419
Ethyl Alcohol 1.361
Cubic Zirconia  2.21
Ice 1.309
Glass (flint)1.66
Water  1.333
Glass (crown) 1.52
Air 1.000 
Refraction
Reflection and Refraction

27. Polarized
Polarizers

28. Another view of polarizing filters

29. Scattered
Earth’s atmosphere contains many molecules and other tiny particles. These particles can scatter sunlight. Scattering means that light is redirected as it passes through a medium.

30. Scattering
The lower the sun is on the horizon, the more of the atmosphere the light travels through before it reaches Earth’s surface. By this time, most of the blue and green wavelengths of light are scattered, so all we see are reds and oranges.

31. Color
As white light passes through a prism, shorter wavelengths refract more than longer wavelengths, and the colors separate.
This process is called dispersion.

33. A rainbow is an example of dispersion
A rainbow is an example of dispersion. Droplets of water act like prisms. Light slows down and refracts when it enters a raindrop. It refracts again as it exits the raindrop, speeds up, and travels back toward the source of the light.

34. refraction diamond cubic zirconia refraction applet - Google Search
applet diamond refraction - Google Search
Molecular Expressions: Science, Optics and You - Refraction of Light: Interactive Java Tutorial

36. Colors of Objects
The color of any object depends on what the object is made of and on the color of light that strikes the object.

37. Primary Colors of Light

38. Secondary Colors of Light

39. Primary Colors of Pigment