What is the approximate surface temperature of a star with moderate hydrogen absorption lines and moderate ionized calcium absorption lines?
A) 4,500 K B) 5,500 K C) 3,500 K D) 6,500 K
D
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When a force is called a "normal" force, it is
A. the usual force expected given the arrangement of a system. B. a force that is perpendicular to the surface of the Earth at any given location. C. a force that is always vertical. D. a contact force perpendicular to the contact surfaces between two solid objects. E. the net force acting on a system.
Which of the following is NOT an argument for Cygnus X-1's being a true black hole?
A) Spectroscopic data suggests hot gas is flowing from the companion B star onto Cygnus X-1. B) The mass of the visible B star is even greater than Cygnus X-1, at around 25 solar masses. C) Cygnus X-1's mass is estimated to be about 10 solar masses. D) X-rays from Cygnus X-1 vary on time scales as short as a millisecond. E) X-ray observations around the object support a temperature of several million K.
When light passes through common windowpane, its angle of emergence is
A) usually less than its angle of incidence. B) always less than its angle of incidence. C) the same as its angle of incidence. D) usually more than its angle of incidence. E) always more than its angle of incidence.
Describe diamagnetism
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