How many stars can you see with your naked eye on a clear, moonless night from a dark location?
A) fewer than a thousand
B) a few thousand
C) about ten thousand
D) about a hundred thousand
E) more than you could count in your lifetime
B
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The spectra of the coolest stars contain strong absorption features (or lines) of
a. TiO molecules.
b. ionized helium.
c. helium.
d. hydrogen.
e. All of the other choices are correct.
Which of the following statements best describes the current state of understanding regarding the apparent acceleration of the expansion of the universe?
A) The cause of the acceleration is well-understood, and attributed to the particles that make up dark energy. B) The acceleration is very important in the cosmos today, but the evidence indicates that it will eventually slow down, allowing the universe to recollapse. C) The acceleration probably is not real, and what we attribute to acceleration is probably just a misinterpretation of the data. D) We have moderately strong evidence that the acceleration is real, but essentially no idea what is causing it.
Einstein won the Nobel Prize for explaining
a. general relativity. b. special relativity. c. the photoelectric effect. d. quantum mechanics.
An atom containing three outer-shell electrons is added to a Group IV semiconductor such as silicon. The result is
1.a p-type semiconductor. 2.an insulator. 3.an n-type semiconductor. 4.a conductor.