Cepheid and RR Lyrae variable stars change their brightness by ____
a. atmospheric explosions of hydrogen gas
b. internal changes in their fusion processes
c. a combination of atmospheric explosions and internal changes
d. a combination of atmospheric explosions and physically pulsating
e. changing its period between pulses
e
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A grating is made with 600 slits per millimeter. What is the slit separation?
A. 600 nm
B. 
C. 
D. 160 pm
E. 916 nm
When you stand at rest on a pair of bathroom scales, the readings on the scales will always
A) each be half your weight. B) each equal your weight. C) add to equal your weight. D) add up to more than your weight.
The condensation theory is an example of:
A) a catastrophic theory. B) a hot Jupiter theory. C) a collision hypothesis. D) an evolutionary theory. E) a capture theory.
How are the speed v of a wave, its wavelength , and its period T related?
a. v = T b. v = - T c. v = 0 d. v = /T e. v = T/