1. E-M Spectrum and Waves
Prentice Hall Chapter 18

2. Chapter Assignments Workbook and E-M Spectrum Activity Book
Section 18.1: 535/math practice 1-3 and 538/9,10
Section 18.2: 545/4, 5, &7
Section 18.5: 562/3-7
565-67/1-10, 32-35, and FCAT practice

3. Review from the last chapter:
Two types of waves are:
Regarding requiring a medium for travel
Mechanical and electromagnetic
Electromagnetic does not require a medium
Regarding shape of the wave
Transverse and longitudinal
Electromagnetic waves are transverse waves

4. Electromagnetic (E-M) Waves (LIGHT!)
Do not require a medium through which to travel
Light travels at 3.0 x 108 m/s in a vacuum or air
Its wavelength and frequency varies according to the type of E-M wave

5. Higher frequency 
Greater energy 
More penetration
The full range of frequencies of electromagnetic radiation is called the electromagnetic spectrum.
Again, all of these forms move at 3.0 x 108 m/s in a vacuum (space) or air.
One type to the left of another type has a longer wavelength and a lower frequency. For instance: radio waves have a longer wavelength than infrared.
Blue light has a higher frequency than red light.
Electromagnetic waves vary in wavelength and frequency

6. Properties of E-M Waves (Light)
Light can act as a wave or a particle
Only a very small portion of the E-M Spectrum is visible to humans (between infrared rays and ultraviolet rays)
Those types to the right of the visible portion are more penetrating and harmful (can be used to “look inside” or pass through objects); i.e., x rays and gamma rays

7. c = f l c = ?
This formula is used to determine information about light.
Let’s say that you know the wavelength of yellow light is 600 x 10-7 m. What is its frequency? Using c = f l
f = c/ l
f = 3.0 x 108 m/s / 600 x 10-7 m
f = 3/600 x = x 1015
f = 5 x 10-3 x 1015 = 5 x = 5x1012 Hz

8. Another problem
Find the frequency of an electromagnetic wave in a vacuum with a wavelength of 0.02m
f = c/ l
f = 3.0 x 108 m / 0.02 m
f = 1.5 x 1010 Hz
Assignment:
535/math practice 1-3 and 538/9,10

9. Behavior of Light Materials can affect the behavior of light
Transparent materials allow most light to pass through
Translucent materials scatter light and makes figures appear unclear in appearance
Opaque materials either absorb or reflect all of the light that hits them. No light can pass through.

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

11. Reflection
When you look into a mirror, light reflects from the mirror, and you see yourself
Because of total internal reflection, laser light can travel inside small glass (optical) fibers and carry information

12. Refraction
Bending of light as it passes from one medium into another. It makes the pencil look broken.

13. Newton and Prisms
When white light passes through a prism you see a rainbow, because of refraction:
Different colors bend at different angles
A rainbow is formed when water droplets in the air disperse light.

14. Colors of objects
Is dependent upon what the object is made of and on the color of light that strikes the object.
See figure 24 (page 552) in your book

15. Primary Colors Primary colors of light are Red, green, blue
pigment are
Magenta, cyan,
and yellow
(See page 552
In your book)

16. Red, blue, and green light added together produce white light.
R, blue, and green are primary colors of light
Red plus green produce yellow, a secondary color
Since yellow contains both red and green, when you add yellow to blue, you get white light!
What about cyan and red?
Since cyan contains green and blue, when you add red, you get white light again!

17. Mixing
Mix colors of light together, you get more light - additive process
*Mix complementary colors
of light  white light (blue
& yellow or green & magenta)
*Complementary colors
are opposite each other
in the color wheel.

18. Mix colors of pigment together, you get less light (it’s absorbed) - subtractive process.
The primary colors
of pigment are the
secondary colors
of light!

19. Assignments: Section 18.2: 545/4, 5, &7 Section 18.5: 562/3-7
565-67/1-10, 32-35, and FCAT practice

20. Other tidbits about light:
Microwaves are used to communicate between cell phones
Light is produced in the filament of an incandescent light bulb when electrons flow through the filament
Sodium-vapor lights are used for lighting many streets and parking lots
Fluorescent light tubes usually contain mercury vapor (which give off invisible uv light causing phosphors to emit visible light)

21. Light shining on objects
See page 552
What an object is made of and the color of light that strikes it determine the apparent color of the object.
In white light all colors of the object are evident
When other colors of light shine on the object, the colors appear very different.

22. Laser Light
Laser stands for Light Amplification by Stimulated Emission of Radiation.
Laser light is coherent - all the waves have the same: wavelength, direction, and coincidental peaks. This means IT IS VERY INTENSE & CAN BE HARMFUL!!!

23. Light - wave or particle?
A wave when light interferes either constructively or destructively
Light is turned “on” by constructive interference and “off” by destructive interference resulting in an interference pattern (shown at left).

24. Light acts as a particle when…
Electrons are emitted from a metal caused by light striking the metal during the PHOTOELECTRIC EFFECT
Examples:
Light sensors in cameras, video cameras, automatic doors.
Newton said it acted as particles because it travels in a straight line and casts shadows.

25. Polarization
Only the blue waves can pass through the opening in the first card but not through the 2nd card.

26. Infra- and Ultra-
Infra- means under, so infrared light is under red light (or to the left in the E-M spectrum)
Ultra- means above, so ultraviolet light is above violet light (or to the right in the E-M spectrum)

27. Sources concise.britannica.com/ebc/art-70892/The-spec...
Frames 3 & 4
concise.britannica.com/ebc/art-70892/The-spec...
Frame 11
hyperphysics.phy-astr.gsu.edu/.../refr2.html
Frame 12
Frame 13
Frame 17
hyperphysics.phy-astr.gsu.edu/.../lassol.html
Frame 18