Why is the sky blue (on Earth)?
A) because the Sun emits mostly blue light
B) because molecules scatter red light more effectively than blue light
C) because deep space is blue in color
D) because molecules scatter blue light more effectively than red light
E) No one knows—this is one of the great mysteries of science.
D
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A refrigerator uses mechanical work to transfer heat from a colder region to a hotter one, as shown in this schematic. Why is it not possible to remove heat from the cold region and transfer it to the hot region without the input of work by an external source?
a. It would violate the first law of thermodynamics. b. It would violate the second law of thermodynamics. c. Both a. and b. d. It would be possible only if the machine did not lose some energy as heat because of friction.
What is the minimum thickness of a coating of magnesium fluoride (n = 1.38) applied to glass (n = 1.50) that gives a minimum reflection for 600 nm light?
A. 600 nm B. 300 nm C. 435 nm D. 109 nm E. 100 nm
If a block is set sliding on a huge imaginary frictionless plane in contact with Earth's surface, it will NOT sustain a constant speed because
A) a component of gravitational force parallel to the plane soon acts on it. B) gravity gets weaker as distance increases. C) it is not free from the shackles of Earth's gravity. D) of its inertia.
A DC current of size 10 A flows through one coil of a transformer. What is the current flowing through the other coil of the transformer if that second coil has ten times as many loops as the first?
a. 0 A b. 1.0 A c. 10 A d. 100 A e. 1000 A