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Summary: Physics 314 (Survey of Astronomy) Exam 1
Please show all significant steps clearly in all problems.
Please give clear and legible responses to qualitative questions.
See the last page for values of constants.
1. Nuclear reactions in stars
(a) (3) Write down the proton-proton chain of reactions that converts H to He, being careful to show all
the particles in each reaction.
(b) (3) Write down the triple alpha set of reactions that converts He to C. What qualitative statement can
you make about the lifetime of 8
Be and its significance?
(c) (3) Why does fusion produce energy for light elements, and fission for heavy elements?
(d) (3) What is the heaviest element that can be produced in normal fusion reactions in stars, and why?
(e) (3) How are heavier elements produced, with larger atomic numbers Z ? E.g., how were the selenium
( Z = 34 ) and iodine ( Z = 53) in your body produced?
2. Some simple ideas
(a) (2) Why does a solar eclipse not occur whenever there is a new moon, and a lunar eclipse whenever
there is a full moon?
(b) (3) By considering a rotating frame of reference, with a (fictitious) centrifugal force, explain how the
Sun produces tides. (The same principle applies with the more important influence of the Moon, but let us
consider only the Sun here for simplicity.) It may help to draw a picture.
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