GRE Subject Test: Physics : Special Topics

Study concepts, example questions & explanations for GRE Subject Test: Physics

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All GRE Subject Test: Physics Resources

33 Practice Tests Question of the Day Flashcards Learn by Concept

Example Questions

Example Question #1 :Astrophysics

If the temperature of a blackbody doubles, what occurs to the wavelength of maximum emission?

Possible Answers:

It is quartered.

It is halved.

It quadruples.

It doubles.

No change.

Correct answer:

It is halved.

Explanation:

This is an application of Wein's Law that states the following:

, whereis the wavelength of maximum emission of the object (measured in), andis the temperature in.自从wavelength and the temperature are inversely proportional, if we double the temperature, we must cut the wavelength by the same proportion. Therefore, the temperature must be halved.

Example Question #1 :Astrophysics

By what factor will the energy emitted each second off the surface of a blackbody change if the the temperature of the object is tripled?

Possible Answers:

Correct answer:

Explanation:

Stefan-Boltzmann's equation for a blackbody states:

, whereis the energy emitted each second,is the Stefan-Boltzmann constant, andis the temperature of the blackbody. Therefore, if we triple the temperature, the energy will increase by a factor of

Example Question #1 :Astrophysics

Using the kinetic theory of gas, what is the fundamental property of a planet that dictates if it is able to retain an atmosphere?

Possible Answers:

Number of moons

Temperature

Energy

Mass

Magnetic field strength

Correct answer:

Mass

Explanation:

The kinetic theory of gas states:

.Whenever the velocity of the individual gas particles is larger than the escape speed of the planet,

, the gas particles will leak into space and deplete the atmosphere. The physical property that determines this is the mass of the planet.

All GRE Subject Test: Physics Resources

33 Practice Tests Question of the Day Flashcards Learn by Concept
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