A highly reliable laser emits a steady beam of light at a fixed frequency f that hits a photodetector a light year away in what we can assume is empty space. The laser/detector setup is now placed as a system with a black hole directly behind the laser. What happens to the frequency of the light beam?
a.
The laser emits the same light at its position because nothing changes with respect to the laser. One can imagine the light being stretched as it climbs out of the potential well of the black hole. A longer wavelength means a lower frequency of light. This is called gravitational redshift, because the light loses energy due to gravity and shifts toward the red end of the spectrum.
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Collisions in Two Dimensions: A 900-kg car traveling 30.0° south of east at 12.0 m/s suddenly collides with a 750-kg car traveling north at 17.0 m/s. The cars stick together after colliding. What is the speed of the wreckage just after the collision?
A. 7.21 m/s B. 12.2 m/s C. 20.4 m/s D. 25.0 m/s E. 17.3 m/s
That Polaris will not always be the pole star is due to
A) the sidereal day being shorter than the solar day. B) precession shifting the celestial pole. C) the Moon following the ecliptic, instead of the equator. D) the Earth's revolution being slightly less than exactly 365.25 days. E) the Solar winds blowing the Earth farther away from the Sun.
Gamma rays are emitted by way of
A) ionizing radiation. B) transitions within an atom's innermost electrons. C) transitions within the atomic nucleus. D) none of the above
Which of these statements about the poles of magnets is correct?
a. Like poles repel; unlike poles attract. b. Like poles attract; unlike poles repel. c. Unlike poles attract; like poles have no effect. d. All poles repel. e. All poles attract.