### All GRE Subject Test: Physics Resources

## Example Questions

### Example Question #1 : Quantum Mechanics And Atomic Physics

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

**Possible Answers:**

Infared

Gamma-rays

Red light

Radio

X-ray

**Correct answer:**

Gamma-rays

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 : Quantum Mechanics And Atomic Physics

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

**Possible Answers:**

X-ray

Gamma-ray

Red light

Radio

Infrared

**Correct answer:**

Radio

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.

### Example Question #1 : Square Wells/Particle In A Box

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

**Possible Answers:**

At the boundary.

In the middle.

the way in the box.

the way in the box.

None of these

**Correct answer:**

At the boundary.

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).

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