Light from a laser is
1) monochromatic.
2) in phase.
3) coherent.
4) all of the above.
Compared to the energy put into a laser, the energy of the laser beam is
5) usually much more.
6) much less.
7) the same.
Answer: 4, 6
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Doppler Effect: A train is traveling away from you at 120 km/h. It blows its whistle, and you hear a tone of 0.400 kHz. Take the speed of sound to be 340 m/s. What frequency does the whistle actually produce?
A. 444 Hz B. 439 Hz C. 364 Hz D. 361 Hz
The figure shows two forces acting at right angles on an object. They have magnitudes = 6.3 N and = 2.1 N. What third force will cause the object to be in equilibrium (acceleration equals zero)?
A) 6.6 N at 162° counterclockwise from 1 B) 6.6 N at 108° counterclockwise from 1 C) 4.2 N at 162° counterclockwise from 1 D) 4.2 N at 108° counterclockwise from 1
The lift experienced by a helicopter involves an action-reaction pair of forces between the
A) helicopter blades and the air. B) mass of the helicopter and Earth's mass. C) weight of the helicopter and atmospheric pressure. D) motion of the helicopter relative to the ground below. E) any or all of the above
Suppose that the force of gravity between the sun and Earth suddenly stopped operating. What would happen?
A) Earth would stop in its orbit around the sun, and remain motionless at its present position. B) Earth would continue orbiting the sun, but objects on Earth would have no weight and would float into space. C) Earth would fall directly inward, into the sun. D) Earth would fly directly outward from the sun. E) Earth would move straight ahead, in a straight line, rather than orbiting the sun.