Which of the following is not consistent with observations of the cosmic microwave background?
A) The universe is at least 20 billion years old.
B) The universe is geometrically "flat" (in the four dimensions of spacetime).
C) Dark energy, whatever it is, represents the majority of the energy content of the universe.
D) The matter density (both luminous and dark matter combined) in the universe is only about one-fourth of the critical density.
A
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High-mass stars have ________ lifetimes than low-mass stars.
A) much shorter B) slightly shorter C) much longer D) slightly longer
A ball is thrown at an angle 45.0° above the horizontal from ground level with an initial velocity of 20.0 m/s. What is the range of the ball?
A) 20.0 m B) 40.8 m C) 19.6 m D) 34.4 m E) None of the other choices is correct.
Voltage can also be called
a. potential b. pressure c. work d. energy e. none of the above
Refer to the figure above. Suppose that an electron makes a transition from n = 3 to n = 2 and emits a photon of frequency 4 × 1014 Hz. Then an electron that makes a transition from n = 3 to n = 1 may emit a photon with a frequency of
1) 1 × 1014 Hz, 2) 3 × 1014 Hz, 3) 4 × 1014 Hz, 4) 9 × 1014 Hz, which is consistent with emission of the most energetic photon from a transition from n = 3 to 5) n = 1. 6) n = 2. 7) either, as both transitions are equivalent.