When can Sirius, a favorite star of the Northern Hemisphere, be observed?
a. during summer
b. during spring
c. all year long
d. during winter
e. during fall
d
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Electromagnetic wavelengths of a few centimeters are classified as in what range?
A. visible B. ultraviolet C. microwave D. radio E. gamma ray
A shift in the position of an emission line of an element toward the red or blue is produced by ____
a. atoms that become ionized b. electrons that transfer from a high energy level to a low energy level c. electrons that transfer from a low energy level to a high energy level d. the intensity of agitation of atoms in a hot gas e. the motion of an object toward or away from the observer
The diagram above shows the life track of a 1 MSun protostar from the time it first begins to form until it reaches the main sequence, with four stages labeled. What is happening to the protostar's surface temperature and luminosity during Stage 2, when it is undergoing convective contraction, and its life track moves almost straight down on the HR diagram?
A) Its surface temperature and luminosity increase. B) Its surface temperature remains the same and its luminosity decreases. C) Its surface temperature and luminosity decrease. D) Its surface temperature decreases and its luminosity increases. E) Its surface temperature and luminosity remain the same.
Two blocks of masses m1 and m2 are released from the top of two frictionless inclined planes of the same height making 30° and 60° angles with the horizontal direction, respectively
Which of the blocks is going faster when it reaches the bottom of its respective incline? A) We must know the actual masses of the blocks to answer. B) Both blocks have the same speed at the bottom. C) Block 1 is faster. D) Block 2 is faster. E) There is not enough information to answer the question.