Which stars spend the shortest amount of time as protostars?
A) the most massive stars
B) the least massive stars
C) Mass doesn't matter, all stars spend about the same amount of time as protostars.
A) the most massive stars
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Werner Heisenberg's main contribution to the development of quantum theory was
A) the nonlocality principle. B) his explanation of the photoelectric effect, in terms of photons. C) a method for predicting the position at which electrons or other particles will strike the viewing screen in such experiments as the electron double-slit experiment. D) a method for predicting the overall statistical patterns that appear in the electron double-slit experiment and other experiments using microscopic particles. E) the uncertainty principle.
A compound microscope gives a magnification of 200? with an eyepiece of focal length 2.00 cm. If the eyepiece is replaced with an eyepiece of focal length 1.50 cm, what magnification results?
a. 
b. 
c. 
d. 
e. 
What is the absolute magnitude of our Sun?
A) -23.0 B) -4.6 C) -1.4 D) +4.8 E) +9.4
A fish is 80 cm below the surface of a pond. What is the apparent depth (in cm) when viewed from a position almost directly above the fish? (For water, n = 1.33.)
A. 50 B. 60 C. 40 D. 70 E. 110