Suppose we observe a Cepheid variable in a distant galaxy. The Cepheid brightens and dims with a regular period of about 10 days. What can we learn from this observation?
A) the distance to the galaxy
B) the rotation rate of the galaxy
C) the mass of the galaxy
D) the name of the galaxy
A) the distance to the galaxy
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When the electric field vibrations of a light
wave are restricted to one direction, the wave has been a) dispersed. b) diffused. c) diffracted. d) polarized.
A laser beam (? = 694 nm) is incident on two slits 0.100 mm apart. Approximately how far apart (in m) will the bright interference fringes be on the screen 5.00 m from the double slits?
a. 3.47 × 10^?3 b. 3.47 × 10^?2 c. 3.47 × 10^?4 d. 3.47 × 10^?6 e. 3.47 × 10^?5
What evidence suggests that most of the mass of the Milky Way is in the form of dark matter?
A) The orbital speeds of stars far from the galactic center are surprisingly high. B) Although dark matter emits no visible light, we have detected its radio emissions. C) Theoretical models of galaxy formation suggest that a galaxy cannot form unless it has at least 10 times as much matter as we see in the Milky Way disk. D) Our view of distant galaxies is often obscured by dark blotches, which are presumably made of dark matter.
Calculations show that gravity begins to overcome thermal pressure in clouds that are
A) less massive than the Sun. B) more massive than the Sun. C) more massive than ten times the Sun. D) more massive than a hundred times the Sun. E) more massive than a thousand times the Sun.