Suppose we observe a source of X-rays that varies substantially in brightness over a period of a few days. What can we conclude?
A) The X-ray source is a quasar.
B) The X-ray source contains a black hole with an accretion disk.
C) The X-ray source is no more than a few light-days in diameter.
D) The X-ray source must have a strong, rapidly varying magnetic field.
E) We are seeing the rapid orbit of two stars in a binary system.
C
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A wave is represented by the equation y(x, t) = 3.2 cm sin(1000 rad/s t - 50
x). Another wave is represented by the equation y(x, t) = 4.2cm sin(1000 rad/s t - 50
x). If the two waves interfere constructively, then what is equation that represents the coherent superposition of the two waves?
A. y(x, t) = 7.4 cm sin(1000 rad/s t + 50.0
x)
B. y(x, t) = 1.0 cm sin(1000 rad/s t - 50.0x)
C. y(x, t) = 1.0 cm sin(1000 rad/s t + 50.0x)
D. y(x, t) = 7.4 cm sin(1000 rad/s t - 50.0x)
The fresh, newly created surfaces of icy satellites of Jovian planets
a. appear dark in color with few impact craters. b. appear dark in color with many impact craters. c. appear very bright because fresh ice is very reflective. d. generally show long bright grooves and a modest number of impact craters. e. generally have small volcanoes that are active.
You observe a distant galaxy. You find that a spectral line of hydrogen that is shifted from its normal location in the visible part of the spectrum into the infrared part of the spectrum. What can you conclude?
A) The galaxy is moving away from you. B) The galaxy is moving toward you. C) The galaxy has weak gravity. D) The galaxy is made purely of hydrogen.
Two long parallel wires carry currents of 20 A and 5.0 A in opposite directions. The wires are separated by 20 cm. At what point between the two wires do they produce the same strength magnetic field?
A) 8.0 cm from the 20 A wire B) 18 cm from the 20 A wire C) 12 cm from the 20 A wire D) 16 cm from the 20 A wire E) 4.0 cm from the 20 A wire