In the standard model, about when after the Big Bang did the universe become transparent to radiation?
A)
10-43 s
B)
10-35 s
C)
103 s
D)
3 × 105 y
E)
3 × 106 y
D
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A soap bubble, when illuminated with light of frequency 5.11 × 1014 Hz, appears to be especially reflective. If it is surrounded by air and if its index of refraction is 1.35,
what is the thinnest thickness the soap film can be? (c = 3.00 × 108 m/s)
A parachutist of mass 50.0 kg jumps out of an airplane at a height of 1 040 m. The parachute deploys, and she lands on the ground with a speed of 4.0 m /s. How much energy was lost to air friction during this jump?
a. 4.0E+2 J b. 8.2E+4 J c. 4.3E+5 J d. 5.1E+5 J e. 6.4E+5 J
The two most abundant elements that make up the salinity of seawater are
A) sodium and potassium. B) chlorine and sulfur. C) calcium and sulfur. D) chlorine and sodium.
A 10-kg block has twice the density of water. Compared to 10 kg of water, its volume is
1) as much, 2) half as much, 3) twice as much, and when suspended in water its mass will seem to be 4) 0 kg. 5) 3.33 kg. 6) 5 kg. 7) 10 kg. 8) none of these.