When Earth was young, its atmosphere had no free ____
a. nitrogen
b. oxygen
c. helium
d. carbon dioxide
e. water vapor
b
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The diagram below represents energy levels in a hydrogen atom. Each level is labeled with its energy (above the ground state of Level 1) in units of electron/volts (eV). The labeled transitions represent an electron moving between energy levels. Which transition, as shown, is not possible?
A) A B) B C) C D) D E) E
Define velocity, and give an example
At temperatures above the equi-cohesive temperature, the creep mechanism of grain boundary _________is observed.
Fill in the blank(s) with the appropriate word(s).
Which produces a brighter image? Choose the best answer
a. a small-diameter telescope b. a large-diameter telescope c. A very small light collector d. None of the other choices are correct.