Tritium has a half-life of 12.3 years. How many years will elapse when the radioactivity of a tritium sample diminishes to 35% of its original value?
a. 1.2E–1 years
b. 1.9E+1 years
c. 4.3E+0 years
d. 6.3E+1 years
e. 8.1E+0 years
b
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A capacitor C is connected in series with a resistor R across a battery and an open switch. If a second capacitor of capacitance 2C is connected in series to the first, the time constant of the new RC circuit will be
A) the same as before. B) larger than before. C) smaller than before. D) variable.
Two motors in a factory are running at slightly different rates. One runs at 825 rpm and the other at 786 rpm. You hear the sound intensity increase and then decrease periodically due to wave interference
How much time elapses between successive maxima of the sound intensity? A) 1.5 s B) 1.4 s C) 1.7 s D) 1.8 s
If the intensity of a sound is increased by a factor of 100, how is the decibel level changed? The new decibel level will be:
a. two units greater. b. double the old one. c. ten times greater. d. twenty units greater.
A laser with a power of 1.0 mW has a beam radius of 1.0 mm
What is the peak value of the electric field in that beam? (c = 3.0 x 108 m/s, ?0 = 4? × 10-7 T ? m/A, ?0 = 8.85 × 10-12 C2/N ? m2) A) 490 V/m B) 22 V/m C) 65 V/m D) 840 V/m E) 120 V/m