1. Test Review for

2.  Light is created by vibrating charged particles  It is a transverse wave  It is the only wave that does not need a medium to travel through.

3.  Time the appearance of the following image:  Symbol is c  3 x 10 8 m/s or  300,000,000 m/s  A constant (when in a vacuum or atmosphere)  Average speed of light slows down in different materials due to time delays between absorption and re-emission within the material (you won’t need to know how to calculate this).

4.  Stop your whining!  Same equations as the last unit  v=d/t  v=λf  This time though, replace the v with c!  c=d/t  c=λf

5.  It takes sunlight 8 minutes to travel to Earth. How far away is the sun?  First convert 8 minutes to seconds  8 minutes x 60 seconds/minute = 480 seconds  Now plug this into d=ct  d=3x10 8 m/s x 4.8x10 2 s  d=1.44 x 10 11 m (144 million kilometers)

6.  What is the frequency of violet light with a wavelength of 400 nm (4 x 10 -7 m)?  Rewrite c=λf to f = c/λ  f = (3x10 8 m/s) / (4x10 -7 m)  7.5 x 10 14 Hz

7.  Created by OPAQUE objects blocking light.  Umbra: dark center, all light is blocked  Penumbra: fuzzy edges, some light is blocked

9.  Technical (read fancy) name for all light, including visible light.  All EM-waves travel at the same speed  They are defined by their different frequencies and wavelengths.

10. Increasing frequency  Decreasing wavelength  Increasing energy 

11.  Objects can be opaque to some EM waves but translucent to others.  Windows:  Can you see through them?  Can you get sunburned through one?  Can infrared pass through them? (Look at the glasses above)

12.  If you double your distance from the light:  The illuminance of the light is quartered.  If you triple your distance from the light:  The illuminance of the light will be 1/9 th of the original brightness  If you halve your distance from the light:  The illuminance of the light is quadrupled.  Illuminance ~ 1/distance 2

13.  Natural light is randomly polarized.  Polarizers block light waves oscillating in one direction.  Reduces brightness of light by 50% for the first polarizer.  Second polarizer at 90 o of first polarizer will block all light.  Reflected light/glare are horizontally polarized

14.  Primary colors - red, blue, green  White objects reflect all light.  Black objects absorb all light.  Blue objects reflect BLUE light and absorb all other light.  All other light colors are made of the three primary colors.  Complementary colors: the two colors that can be added together to make white light.

15. Use of additive colors:

16.  Depends on colored light being subtracted.  Primary colors: magenta, cyan, and yellow.  Absorb one primary color of light and reflects two.  Filters subtract all light except for the color of the filter.  Pigments/dyes absorb all colors except for the few they reflect.

17.  A red shirt under magenta light: red  A green book under blue light: black  Used by: