A point source emits sound waves with a power output of 100 watts. What is the sound level (in dB) at a distance of 10 m?
a. 139
b. 119
c. 129
d. 109
e. 10
d
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In a demonstration, a 4.00 cm2 square coil with 10,000 turns enters a larger square region with a uniform 1.50-T magnetic field at a speed of 100 m/s. The plane of the coil is perpendicular to the field lines. If the breakdown voltage of air is 4000 V/cm on that day, the largest gap you can have between the two wires connected to the ends of the coil and still get a spark is
A. 7.5 × 10?3 cm. B. 0.015 cm. C. 7.5 cm. D. 13 cm. E. 15 cm.
If a wave has a frequency of 15 Hz, it has a period of
a. 1/15 s. b. 3.9 s. c. 225 s. d. 15 s.
In the operation of a laser
a. stimulated emission occurs. b. there is a population inversion. c. the excited state will tend to be metastable. d. the photons emitted will have transitioned to the ground state. e. For the answers (a), (b), (c), and (d), three are correct and one is incorrect.
Which of the following is considered "interplanetary matter"?
A) Titan B) Triton C) the Moon D) Ganymede E) Comet Hale-Bopp