A light-emitting diode (LED) converts electricity to approximately sinusoidal electromagnetic waves with a definite frequency f. Imagine that light from the LED creates an oscillating electric field with amplitude E0 at a certain location. If we increase the electrical power to the LED so that the oscillation amplitude is now 2E0, by what factor have we increased the power?
A. 4 times
B. 2 times
C. 
times
D. One cannot answer without more information.
A. 4 times
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The Doppler technique only provides a measure of the minimum mass of a planet because
A) only a small part of the planet's motion is measured. B) without a transit observation, the size and therefore density of the planet is unknown. C) we do not know the exact composition of the planet. D) only the motion of star toward the observer is measured, not the full motion. E) we do not have the technology to make a direct image of a planet yet.
A solid ball and a hollow ball are released from rest at the top of an incline and roll without slipping to the bottom. Which reaches the bottom first?
A. The solid ball. B. The hollow ball. C. Both will arrive at the same time. D. The result depends on the balls’ relative masses. E. The result depends on the balls’ relative radii. F. The result depends on the ball’s relative masses and their relative radii.
A weak acid is one that does not
a. taste very sour. b. ionize appreciably in water. c. form hydrogen gas when a metal is dropped in. d. neutralize OH- ions.
The primary source of the energy radiated by a star, such as the sun, is
A) fusion reactions in which helium is fused to form iron. B) fusion reactions in which hydrogen is fused to form helium. C) beta decay. D) fission reactions involving uranium. E) alpha decay.