Why is the sky blue (on Earth)?
A) because molecules scatter blue light more effectively than red light
B) because the Sun emits mostly blue light
C) because molecules scatter red light more effectively than blue light
D) because deep space is blue in color
E) No one knows; this is one of the great mysteries of science.
A) because molecules scatter blue light more effectively than red light
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A series circuit consists of a 100-V DC power source, a 100-? resistor, and a variable resistor of resistance R, which varies from 0 to 100 ?. The current in the circuit is
?
?
A. directly proportional to R. B. inversely proportional to R. C. directly proportional to (100 ? + R). D. inversely proportional to (100 ? + R). E. neither directly nor inversely proportional to R or to (100 ? + R).
Our textbook discusses the cosmic calendar, a model of the history of the universe scaled to a single year. The length of time represented by one month on this cosmic calendar is therefore
A) about ten million years. B) about one million years. C) about one billion years. D) about ten billion years. E) about 1000 years.
What beat frequency is produced by 240-Hz and a 246-Hz tuning forks?
A) 6 Hz B) 12 Hz C) 240 Hz D) 245 Hz E) none of the above
The shell model is an example of a
A) physical model. B) conceptual model. C) both a physical and conceptual model. D) None of the above.