The "inverted population" necessary for laser action
A)
refers to the negative energy levels of electrons.
B)
comes from upside-down levels in certain atoms.
C)
refers to the higher energy state being populated more than one below it.
D)
is another way of saying "coherent."
E)
is another way of saying "incoherent."
C
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When you place a sealed can of air on a hot stove, air in the can undergoes an increase in
A) thermal energy. B) temperature. C) pressure. D) all of the above E) none of the above
The positively charged particle inside an atom is the
a. electron b. proton c. neutron d. nucleus e. none of the above
About how many tons of meteorites strike the Earth on a daily basis?
A) 20 tons B) 200 tons C) 2000 tons D) 20,000 tons
The general heliocentric model proposed by Copernicus was appealing, and eventually became preferred, because
A. it explained why we do not observe stellar parallax. B. it was more aesthetically pleasing than the complicated Ptolemaic model. C. it made more accurate predictions than the Ptolemaic model. D. it replaced Earth with the Sun as the center of the solar system.