Homework, September 28, 2006
AST110-6
Due Date: Thursday, October 5, 2006
1. Decide whether each statement makes sense and explain why it does or does not.
(20pt)
a. Chapter 5, Problem 17. If you could view a spectrum of light reflecting off a
blue sweatshirt, you’d find the entire rainbow of color (looking the same as a
spectrum of white light).
b. Chapter 5, Problem 18. Because of their higher frequency, X rays must
travel through space faster than radio waves.
c. Chapter 5, Problem 23. If a distant galaxy has a substantial redshift (as
viewed from our galaxy), then anyone living in that galaxy would see a
substantial redshift in a spectrum of the Milky Way Galaxy.
d. Chapter 5, Problem 28. An observatory on the Moon’s surface could have
telescopes monitoring light from all regions of the electromagnetic spectrum.
2. Chapter 5, Problem 9. (20pt) Why do atoms emit or absorb light of specific wavelengths?
Briefly explain how we can use emission or absorption lines to determine the chemical
composition of a distant object.
3. Chapter 5, Problem 30. (20pt) Energy Level Transition. The following labeled
transitions represent an electron moving between energy levels in hydrogen atom.
Answer each of the following questions and explain your answer.
a. Which transition could represent an atom that absorbs a photon with 10.2 eV
of energy?
b. Which transition could represent an atom that emits a photon with 10.2 eV of
energy?
c. Which transition, as shown, is not possible?
d. Would transition A represent emission or absorption of light? How would the
wavelength of the emitted or absorbed photon compare to that of the photon
involved in transition C? Explain.
Problems 4 and 5 in the next page.
4. Chapter 5, Problem 32. (20pt) The Doppler Effect. In hydrogen, the transition from
level 2 to level 1 has a rest wavelength of 121.6 nm. Suppose you see this line at a
wavelength of 120.5 nm in Star A, at 121.2 nm in Star B, at 121.9 nm in Star C, and
at 122.9 nm in Star D. Which stars are coming toward us? Which are moving away?
Which star is moving fastest relative to us (either toward or away from)? Explain
your answers without doing any calculations.
5. Chapter 6, Problem 24. (20pt) Pattern of Motion: In one or two paragraphs, explain
why the existence of orderly patterns of motion in our solar system should suggest
that the Sun and the planets all formed at one time from one cloud of gas, rather than
as individual objects at different time.