GRE Subject Test: Physics : Fundamental Concepts

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

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All GRE Subject Test: Physics Resources

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Example Questions

Example Question #1 : Fundamental Concepts

Which of the following wavelengths could be used to measure the position of an electron with the greatest accuracy?

Possible Answers:

Radio

Red light

Infared

X-ray

Gamma-rays

Correct answer:

Gamma-rays

Explanation:

The Heisenberg Uncertainty principle states that

Therefore, the smallest wavelength will have the lowest uncertainty in the position. Thus, we must pick the regime of options given which has the lowest wavelength. That is gamma-ray. 

Example Question #2 : Fundamental Concepts

What wavelength will result in the most accurate measurement of the momentum of an electron?

Possible Answers:

Radio

Gamma-ray

X-ray

Infrared

Red light

Correct answer:

Radio

Explanation:

The Heisenberg Uncertainty Principle states that:

 Since the uncertainty in the position is inversely proportional to the uncertainty in the momentum, we need to pick the longest wavelength. Of the options listed, radio has the longest wavelength.  

All GRE Subject Test: Physics Resources

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