MCC PHS 142 M01 Astronomy Homework Ch.6-7      
Adj Prof Astronomy: Sam Wormley <>

Background Material

  Textbook - Read Chapters 6-7
  Textbook -
  Textbook -
    (take the Multiple Choice Quiz for for each chapter)

  Textbook - Glossary, pg G-1 words like: opposition, conjunction

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Homework Problems

Note the answers to the odd (Conceptual Questions, Problems and
Figure-Based Questions) are in the back of your textbook. It is
strongly suggested that you do some of those in every chapter so you
have immediate feedback as how well you are understanding the material.
There are online multiple choice quizzes for each chapter of your
textbook. Goto then click on

  Your book
  Student Edition
  Choose a chapter
  Multiple Choice Quiz

You are expected to do all of your own homework. Statistical patterns
showing copying or collaboration will result in no credit for the
homework assignment for all participants involved. The Code of Academic
Conduct for Iowa Valley Community College District is found in the
Student Handbook.

Physical Science classes require the use of mathematics. If you don't
know algebra, you sould NOT be taking this class. If you need to review,
look at Introduction to Algebra
WolframAlpha is way faster than a scientific calculator.

There is little excuse for turning homework in late. You have a whole
week between classes to read the chapters and do the homework. Homework
one week late - half credit. Two or more weeks late - no credit. Do the
homework during the week, not in class! You got homework questions,
email me 24/7.  Even if you don't have a homework
question, email me anyway!

Problem 1: 
Determine in what constellation, Venus appears to be on your next
Birthday. Note the Right Ascension, in degrees for the first day of
each month, is on the back of your planisphere. The declination is that
of the ecliptic as planets tend to follow the ecliptic. 

Problem 2: 
What is the wavelength of electromagnetic radiation that has a
frequency of 3 x 1016 Hz? In what part of the spectrum does this
radiation occur? Hint: if you use Figure 6.5 on page 105, look at
Appendix 17 on page A-13. One could also use equation (6.2).

Problem 3: 
How close to the Sun would a spacecraft have to go to reach the
distance that the flux of solar energy (intensity of heat and light) is
20 times as large as the solar energy flux at the Earth? Hint:
Think about this--Newton's inverse square law applies. You could
estimate this graphically or you could create and use a formula.

Problem 4: 
Suppose atoms at rest emit visible light with a wavelength of 500 nm.
At what wavelength would the light from the atoms be observed if 
the atoms were moving toward the Earth at a speed of 20,000 km/s?
Hint: Would equation 6.3 be useful as an step toward the answer? 

Problem 5: 
A 4-meter optical telescope operates at a wavelength of 5 x 10-7
meters. How large would an infrared telescope operating at
10-4 m have to be to have the same resolution as the optical 
telescope? Hint: You could create an equation equating ratios.

Problem 6: 
An astronomer observes Mars at opposition using a telescope that has an
aperture of 50 cm (20 inches) in diameter.  The astronomer observes in
visible light at a wave length of 500 nanometers (nm). What is the
smallest feature the astronomer could resolve assuming no degradation
by the Earth's atmosphere. Hint: To do this problem you have to

  o What does it mean that Mars is at opposition?

  o What is the distance between Earth and Mars when Mars is at 

  o What is the angular resolution of the astronomer's telescope?
    Yes you can use equation (6.6) to determine the angular
    resolution. You must keep track of units and convert them so that
    the the numerator and denominator are in the same units.

  o Once you have the angular resolution, either use trig, or the
    small angle equation (3.1) or (3.2) to determine the the smallest
    feature the astronomer could resolve. Show all of your work
    including all units.

Problem 7: 
Use Figure 6.5 to find the wavelength of a radio wave with a
frequency of 106 Hz. Hint: Appendix 17 on page A-13.

Problem 8: 
Using your star wheel (planisphere), determine how many hours and
minutes the star Sirius is above the horizon. 

Problem 9: 
Use Figure 7.4 to find the pressure at an altitude of 20 km.

Problem 10: 
How does the brightness of sunlight at Neptune's distance compare
with the brightness at the Earth? Hint: Newton's inverse square law

Problem 11: 
The half-life of an unstable isotope is 10 years. After what length
of time would there be less than 1% of the original atoms of the
isotope remaining? Hint: There isn't any applicable formula in your
textbook, so you should approach this graphically--Virtical axis being
percent of atoms left and horizontal axis time in units of ten years.