1. Suppose the Earth's orbit was not tilted with respect to its orbital plane. True or False?

We would no longer experience Day and Night --- False

We would see the same stars in the night sky all year around --- False

We would no longer experience changes in the seasons -- True

2. Given that the Earth is around 24,000 miles in circumference and the speed of light is 186,000 miles/sec; how long would it take a photon to circle the Earth?

Suppose that you have .

Try #1:

Units of miles /sec make no sense.

Try #2:

This has the right units and is the right answer.

3. Given Wien's Law:

(a) How would you manipulate this equation to allow you to solve for the temperature of a solid if you are told the radiation from the object peaks at ? ( cm)

(b) What is the temperature?

4. For each of the observers below, label whether they measure a Redshift, Blueshift or Noshift.

1. A -- reshift
2. B -- blueshift
3. C -- blueshift (smaller than B)
4. D -- noshift

5. What time does the new moon rise? -- sunrise

6. Rank the following in order of increasing wavelength (1 - shortest; 6 - longest):

1 X-rays

2 Blue light

3 Red light

4 Infrared

7. What type of spectrum would you expect to see from a gas with all the atoms in their ground state and no background source of radiation?

No spectrum at all -- for the atom to produce light (at least as far as we have discussed it in this class) you need to have some electrons in excited states so a photon can be emitted on de-excitation

8. Suppose the Earth's atmosphere was twice as ``thick'' (that is twice as many molecules and atoms between sea level and the top of the atmosphere) as it is now. The color of the Sun at noon (compared to the real case of our current atmosphere) would be:

a) unchanged b) bluer c) redder

9. Suppose that electron orbits in hydrogen atoms were not ``quantized'', but the electron in a hydrogen atom could occupy any orbit with arbitrary energy. What type of spectrum would you expect from a hot gas of this hypothetical hydrogen?

A continuous spectrum

Michael Bolte
Wed Jan 21 15:15:16 PST 1998