To determine the distance to a Cepheid, we must measure its ________ of pulsation
Fill in the blank(s) with correct word
period
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White light is incident normally on a thin soap film having an index of refraction of 1.34. It reflects with an interference maximum at 684 nm and an interference minimum at 570 nm with no minima between those two values
The film has air on both sides of it. What is the thickness of the soap film? A) 766 nm B) 894 nm C) 627 nm D) 638 nm E) 510 nm
Find the equation 
bt that fits the following data.
A. 
B. 
C. 
D. 
Half-way to the center of a planet of uniform density, your weight compared to that at the surface would be
A) one-quarter. B) one-half. C) three-quarters. D) the same as at the surface. E) zero.
The Laser Interferometer Gravitational-Wave Observatory (LIGO) made the first detection of gravitational waves in 2016. Which of the following best describes the discovery?
A) The detection verified that gravitational waves exist as predicted by the general theory of relativity. B) The detection of gravitational waves was a huge surprise because no one had predicted they would exist prior to their discovery. C) There is still considerable doubt whether LIGO really detected gravitational waves. D) The detection of gravitational waves contradicted predictions made by the general theory of relativity, requiring scientists to revise the theory.