Who first determined that the energy/s emitted by (luminosity of) Cepheid variable stars is larger the longer their period of variation is?
a. Henrietta Leavitt
b. Edwin Hubble
c. John Glenn
d. Carl Sagan
e. Harlow Shapley
a
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Consider a two-slit interference experiment like the one shown in figure Q3.7b. The distance between adjacent bright spots in the interference pattern on the screen (A) increases, (B) decreases, or (C) remains the same if, The spacing between the slits increases.
A. increases B. decreases C. remains the same
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A pulse is described by 
in SI units. What is the velocity of the pulse?
A. 3 m/s in the +x direction B. 2 m/s in the ?x direction C. 2 m/s in the +x direction D. 4 m/s in the ?x direction E. 4 m/s in the +x direction
What are the main constituents of the solar wind? Which travel faster?
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