Astronomy 120

HOMEWORK - Chapter 3

Radiation

Use a calculator whenever necessary.

For full credit, always show your work and explain how you got your answer in full, complete sentences on a separate sheet of paper.

Be careful about units!

Please CIRCLE or put a box around your final answer if it is numerical.

If you wish, you may discuss the questions with friends, but please turn in your own hand-written solutions, with questions answered in your own way.

  1. ChaissonReview and Discussion3.3

What is the relationship between wavelength, wave frequency, and wave velocity?

  1. Chaisson Review and Discussion 3.4

What is diffraction, and how does it relate to the behavior of light as a wave?

  1. Chaisson Review and Discussion 3.8

Compare and contrast the gravitational force with the electric force.

  1. Chaisson Review and Discussion 3.11

What do radio waves, infrared radiation, visible light, ultraviolet radiation, X rays, and gamma rays have in common? How do they differ?

  1. Chaisson Review and Discussion 3.12

In what regions of the electromagnetic spectrum is the atmosphere transparent enough to allow observations from the ground?

  1. Chaisson Review and Discussion 3.13

What is a blackbody? What are the main characteristics of the radiation it emits?

  1. Chaisson Review and Discussion 3.14

What does Wiens’ law reveal about stars in the sky?

  1. Chaisson Review and Discussion 3.15

What does Stefan’s law tell us about the radiation emitted by a blackbody?

  1. Chaisson Review and Discussion 3.16

In terms of its blackbody curve, describe what happens as a red-hot glowing coal cools.

  1. Chaisson Review and Discussion 3.18

How do astronomers use the Doppler Effect to determine the velocities of astronomical objects?

  1. Chaisson Problem 3.3

Estimate the frequency of an electromagnetic wave having a wavelength equal to the size of the period at the end of this sentence. In what part of the electromagnetic spectrum would such a wave lie?

  1. Chaisson Problem 3.4

Normal human body temperature is about 37oC. What is this temperature in kelvins? What is the peak wavelength emitted by a person with this temperature? In what part of the spectrum does this lie?

  1. Chaisson Problem 3.7

The sun has a temperature of 5800 K, and its blackbody emission peaks at a wavelength of approximately 500 nm. At what wavelength does a protostar with a temperature of 1000 K radiate most strongly?

  1. Chaisson Problem 3.8

Radiation from the nearby star Alpha Centauri is observed to be reduced in wavelength (after correction for Earth’s orbital motion) by a factor of 0.999933. What is the recession velocity of Alpha Centauri relative to the sun?

15.Frequency and wavelength of light are related by:

where is the frequency in units of cycles per second (Hertz)

is the wavelength in meters

is the speed of light in meters/second

a) The wavelength of red visible light is meters. What is its frequency?

b) The frequency of X-rays is about Hertz. What is the

wavelength of X-rays in angstroms if 1 angstrom (Å)

meters?