Most galaxies we see are moving away from us. How do we know this?
a) Light we receive from each galaxy has a longer wavelength than we expect.
b) Each galaxy appears visibly smaller as time passes.
c) We can see that the galaxies are getting dimmer from year to year.
d) Light we receive from each galaxy has a shorter wavelength than we expect.
a) Light we receive from each galaxy has a longer wavelength than we expect.
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A hollow conducting sphere of radius 12 cm had a charge of 18 
C placed on it. What is the potential 20 cm from the center of the sphere?
A. 0 V
B. 15 V
C. 73 V
D. 
E. 
Density waves may explain
A) the lack of blue stars in the halo. B) the random orbits of halo stars. C) the density of red stars in the bulge. D) the spiral arm structure of the Galaxy. E) the large number of open clusters in the halo.
The gas, C3H8, is used in outside grills, and several moles of this gas will burn during an afternoon's grilling. What is the mass of one molecule of this gas?
a. 4.4 × 10^–23 g b. 7.3 × 10^–23 kg c. 7.3 × 10^–26 kg d. 8.8 × 10^–26 kg
Microscopes are inherently limited by the wavelength of the light used. How much smaller (in order of magnitude) can we "see" using an electron microscope whose electrons have been accelerated through a potential difference of 50 000 V than using red light (500 nm)?
a. 3 b. 4 c. 5 d. 6 e. 14