Quantum Mechanics

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GRE Subject Test: Physics › Quantum Mechanics

Questions 1 - 6
1

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

Radio

Red light

X-ray

Gamma-ray

Infrared

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.

2

If a ground state particle is in a one-dimension square well, where is the probability of finding the particle equal to zero?

At the boundary.

In the middle.

the way in the box.

the way in the box.

None of these

Explanation

This is a fundamental concept question. For a ground state particle, the only place where the probability is equal to zero is at the boundary because the particle cannot be found there. He has to be in the box (not unlike a cat).

3

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

Radio

Red light

X-ray

Gamma-ray

Infrared

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.

4

If a ground state particle is in a one-dimension square well, where is the probability of finding the particle equal to zero?

At the boundary.

In the middle.

the way in the box.

the way in the box.

None of these

Explanation

This is a fundamental concept question. For a ground state particle, the only place where the probability is equal to zero is at the boundary because the particle cannot be found there. He has to be in the box (not unlike a cat).

5

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

Gamma-rays

Infared

Radio

X-ray

Red light

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.

6

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

Gamma-rays

Infared

Radio

X-ray

Red light

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.

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