Question 1

A heated blackbody emits electromagnetic radiation over a range of frequencies. According to Wien's displacement law, what happens to the peak frequency $$f_{	ext{peak}} of $$the emitted radiation as the temperature $$T$$ increases?

Accepted Answer

It increases proportionally to temperature.

Question 2

Classical physics predicted that the energy radiated by a blackbody at high frequencies would be infinite (the 'ultraviolet catastrophe'). Which law resolved this issue by quantizing electromagnetic energy?

Accepted Answer

Planck's law

Question 3

A photon of ultraviolet light has a higher frequency than a photon of infrared light. According to the equation $$E = h f$$, which photon has more energy?

Accepted Answer

The ultraviolet photon

Question 4

In the photoelectric effect, electrons are ejected from a metal only if the incident light has a frequency above a certain cutoff $$f_0. $$What is the minimum energy required to eject an electron called?

Accepted Answer

Work function

Question 5

A metal surface with a work function $$W_0$$ = \frac{hc}{550\ 	ext{nm}}$$ is struck with blue light ($$\lambda = 450\ 	ext{nm}$$). If the blue light is replaced by red light ($$\lambda = 700\ 	ext{nm}$$) of the same intensity, what happens?

Accepted Answer

No electrons are emitted

Question 6

Which of the following best describes the Compton effect?

Accepted Answer

Scattering of a photon by an electron resulting in a change in wavelength

Question 7

The Compton shift formula is $$\Delta \lambda = \lambda' - \lambda = \frac{h}{m_e c}(1 - \cos 	heta). $$What does $$	heta$$ represent in this equation?

Accepted Answer

The angle between the incident and outgoing photon directions

Question 8

According to the de Broglie hypothesis, what is the wavelength $$\lambda$$ associated with a particle of mass $$m$$ and velocity $$v$$?

Accepted Answer

$$\lambda = \frac{h}{mv}$$

Question 9

An electron and a proton have the same speed. Which has the longer de Broglie wavelength?

Accepted Answer

The electron

Question 10

An electron and a proton have the same momentum. Which has the longer de Broglie wavelength?

Accepted Answer

Both have the same wavelength

Question 11

An electron and a proton are accelerated through the same voltage. Which has the longer de Broglie wavelength?

Accepted Answer

The electron

Question 12

The Heisenberg uncertainty principle states that the product of the uncertainties in position and momentum is at least $$\frac{h}{2\pi}. $$Which equation expresses this relationship?

Accepted Answer

$$\Delta x \Delta p_x \geq \frac{h}{2\pi}$$

Question 13

In the Davisson-Germer experiment, electrons are scattered off a nickel crystal and produce a diffraction pattern. What does this experiment demonstrate?

Accepted Answer

Electrons can exhibit wave-like properties

Question 14

If the intensity of light striking a metal in the photoelectric effect is increased (without changing the wavelength), what happens to the number of emitted electrons?

Accepted Answer

The number of emitted electrons increases

Question 15

A solar panel uses the photoelectric effect to generate electricity. If the incident light has a frequency below the cutoff frequency of the panel's material, what will happen?

Accepted Answer

No electrons will be ejected

Question 16

Which equation gives the kinetic energy $$K of $$electrons ejected in the photoelectric effect?

Accepted Answer

$$K = h f - W_0$

Question 17

A beam of X-rays is scattered by electrons in a material. The outgoing X-rays have a longer wavelength than the incoming X-rays. What physical principle explains this observation?

Accepted Answer

Compton effect

Question 18

Which of the following statements about photons is correct?

Accepted Answer

Photons have zero rest mass and always travel at the speed of light

Question 19

A scientist wants to determine the temperature of a distant star using its color. Which law should they use?

Accepted Answer

Wien's displacement law

Chapter 30: Quantum Physics – Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards