- What are comets?
- Reading: Chapter 17
*Interplanetary Vagabonds*, Section 17-7. - Questions: 10.

- Reading: Chapter 17
- Where are we in the universe?
- Reading: Chapter 26
*Galaxies*, Introduction and Section 26-1. - Questions: 1 and 2.

- Reading: Chapter 26
- What is the universe made of?
- Reading: Chapter 5
*The Nature of Light and Matter*, Section 5-6. - Questions: 14.

- Reading: Chapter 5
- What is light, and how is it made?
- Reading: Chapter 5
*The Nature of Light and Matter*, Sections 5-1, 2,3,4,5,7. - Questions: 1,4,5,6,7,13,16.

- Reading: Chapter 5
- How does the Doppler effect tell us about motion of objects that emit light?
- Reading: Chapter 5
*The Nature of Light and Matter*, Sections 5-8. - Questions: 17.

- Reading: Chapter 5

Grader: Di Fidio

- 5-1)
`Appproximately how many times around the world could a beam of light travel in one second.`- The speed of light is c = 3 x 10
^{8}m/s. - Thus in one second a light signal can go a distance d = 3 x 10
^{8}m. - The circumference of the earth is about a = 4 x 10
^{7}m.- The circumference of the Earth is Pi (3.14) times the diameter of the Earth, given in the Appendix 2 of our book.
- diameter = 12,756 km.
- circumference = 3.14 x 12765 km = 40,074 km.
- 40,000 km = 4 x 10
^{4}km = 4 x 10^{4}x 10^{3}m = 4 x 10^{7}m.

- Thus the light signal can go n = d/a times around the Earth in one second:
n = 3 x 10

^{8}m/ 4 x 10^{7}m = 0.75 x 10^{1}= 7.5

- The speed of light is c = 3 x 10
- 5-5)
`A light source emits infrared radiation at a wavelength of 825 nm. What is the frequency of this radiation?`- 1 nanometer (nm) is 10
^{-9}meter. - Thus the wavelength is 825 x 10
^{-9}m. - The frequency is the number of waves that go by per second. It
equals the speed of light divided by the wavelength of the light:

- We calculate
- frequency = c/wavelength
- = (3 x 10
^{8}m/s)/(825 x 10^{-9}m) - = (3 x 10
^{8}m/s)/(0.825 x 10^{-6}m) - = 3.6 x 10
^{14}Hz

- 1 nanometer (nm) is 10
- 5-6)
`Announcers at a certain radio station say that they are at ``103.3 FM on your dial,'' meaning that they tansmit at a frequency of 103.3 MHz. What is the wavelength of the ratio waves from this station?`- 1 MHz is 10
^{6}Hz. - Thus the frequency is 103.3 x 10
^{6}Hz. - The wavelength
equals the speed of light divided by the frequency of the wave:

- We calculate
- wavelength = c/frequency
- = (3 x 10
^{8}m/s)/(103.3 x 10^{6}Hz) - = (3 x 10
^{8}m/s)/(1.033 x 10^{8}(1/s)) - = 3 m

- 1 MHz is 10

Davison E. Soper, Institute of Theoretical Science, University of Oregon, Eugene OR 97403 USA soper@bovine.uoregon.edu