A ruby laser beam (l = 694.3 nm) is sent outwards from a 2.7-m diameter telescope to the moon, 384,000 km away. What is the radius of the big red spot on the moon?
a. 500 m
b. 250 m
c. 120 m
d. 1.0 km
e. 2.7 km
C
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You observe two stars that are identical to our Sun, but that are located at di?erent distances from Earth. Which star is the most luminous?
A) They are both the same luminosity. B) The one that appears brightest in our sky is more luminous. C) The one that appears faintest in our sky is more luminous. D) There is no way to tell from the information given.
Two objects attract each other gravitationally. If the distance between their centers is cut in half, the gravitational force
A) is cut to one fourth. B) is cut in half. C) doubles. D) quadruples E) remains the same
The two most plentiful elements in the universe are
A) hydrogen and oxygen. B) nitrogen and helium. C) carbon and oxygen. D) lithium and helium. E) hydrogen and helium.
If ? = 4, which one of the following is a possible quantum number for n?
A) 0 B) 2 C) 3 D) 4 E) 8