In order for the cosmic microwave background to show hydrogen absorption lines at the redshift corresponding to the universe's age of 380,000 years, what condition would have been necessary?
A) There would have needed to be even warmer hydrogen clouds (which would contradict the observation of a uniform temperature in all directions).
B) There would have needed to be cooler hydrogen clouds (which would contradict the observation of a uniform temperature in all directions).
C) There would have needed to be ionized hydrogen (which would contradict the idea that the CMB originates at the time the universe cooled enough for protons and electrons to combine, making neutral atoms).
B
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Interference: Two beams of coherent light start out at the same point in phase and travel different paths to arrive at point P. If the maximum destructive interference is to occur at point P, the two beams must travel paths that differ by
A. a whole number of wavelengths. B. an odd number of half-wavelengths. C. a whole number of half-wavelengths.
When the distance between a pair of charged particles is doubled, the force between them becomes how strong?
An atomic nucleus has a charge of +40e. What is the magnitude of the electric field at a distance of from the center of the nucleus? (k = 1/4??0 = 8.99 × 109 N ? m2/C2,
e = 1.60 × 10-19 C) A) 5.4 × 10-8 N/C B) 5.6 × 10-8 N/C C) 5.8 × 10-8 N/C D) 6.0 × 10-8 N/C E) 6.2 × 10-8 N/C
What is the process of accretion?
A) the separation of materials in a protoplanet by density, with dense material in core B) growth of an object by the accumulation of matter C) the breakup of large objects by violent collisions with other similar-sized objects D) the period of time during which the Sun swept away all the excess material in the solar nebula E) the process by which the solar nebula became heated during its collapse