Q: The work function $$E_0 of a $$metal is $$2.36\ \mathrm{eV}. $$What is the threshold frequency $$f_0$$ for photoemission from this metal? ($$h = 4.136 \times 10$$^{-15}$$\ \mathrm{eV\cdot s})$$

$$5.71 \times 10$$^{14}$$\ \mathrm{Hz}$$

Question 1

Which of the following best describes the energy of a photon with wavelength $$\lambda$$?

Accepted Answer

$$E = hf$$

Question 2

A laser emits light with a wavelength of $$650\ \mathrm{nm}$$ and a power output of $$1.56\ \mathrm{W}. $$How many photons are emitted per second? (Use $$h = 6.626 	imes 10$$^{-34}$$\ \mathrm{J\cdot s}$$ and $$c = 3.00 	imes 10^8$\ \mathrm{m/s})$$

Accepted Answer

$$5.1 	imes 10$$^{18}$$

Question 3

Which of the following statements about the photoelectric effect is correct?

Accepted Answer

Electrons are emitted only if the light frequency exceeds a threshold frequency.

Question 4

The work function $$E_0 of a $$metal is $$2.36\ \mathrm{eV}. $$What is the threshold frequency $$f_0$$ for photoemission from this metal? ($$h = 4.136 	imes 10$$^{-15}$$\ \mathrm{eV\cdot s})$$

Accepted Answer

$$5.71 	imes 10$$^{14}$$\ \mathrm{Hz}$$

Question 5

If the intensity of monochromatic light is reduced but the wavelength remains the same, what happens to the number of photons arriving per second?

Accepted Answer

It decreases.

Question 6

A photon of green light has a wavelength of $$520\ \mathrm{nm}. $$What is its energy in electron volts? ($$h = 4.136 	imes 10$$^{-15}$$\ \mathrm{eV\cdot s}$$, $$c = 3.00 	imes 10^8$\ \mathrm{m/s})$$

Accepted Answer

$$2.4\ \mathrm{eV}$$

Question 7

Which of the following best describes the momentum of a photon?

Accepted Answer

$$p = \frac{E}{c}$$

Question 8

In the photoelectric effect, what is the maximum kinetic energy $$K_{	ext{max}} of an $$emitted electron?

Accepted Answer

$$K_{	ext{max}} = hf - E_0$

Question 9

A metal has a work function of $$4.28\ \mathrm{eV}. $$What is the longest wavelength of light that can cause photoemission from this metal? ($$h = 4.136 	imes 10$$^{-15}$$\ \mathrm{eV\cdot s}$$, $$c = 3.00 	imes 10^8$\ \mathrm{m/s})$$

Accepted Answer

$$290\ \mathrm{nm}$$

Question 10

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

Accepted Answer

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

Question 11

An electron is released from the negative plate and accelerates toward the positive plate. How does its de Broglie wavelength change as it reaches the positive plate?

Accepted Answer

It decreases.

Question 12

In the Bohr model of the hydrogen atom, what is the quantization condition for the electron's angular momentum?

Accepted Answer

$$L = n\hbar$$

Question 13

What is the energy of the ground state ($$n=1) of $$the hydrogen atom according to the Bohr model?

Accepted Answer

$$-13.6\ \mathrm{eV}$$

Question 14

A hydrogen atom absorbs a photon and its electron transitions from $$n=1 to$$ $$n=3. $$What is the energy of the absorbed photon?

Accepted Answer

$$E = -13.6\ \mathrm{eV} - (-1.51\ \mathrm{eV})$$

Question 15

Which of the following is true about the emission spectrum of hydrogen?

Accepted Answer

It consists of discrete lines corresponding to transitions between energy levels.

Question 16

If the work function of a cathode is increased, what happens to the threshold frequency for photoemission?

Accepted Answer

It increases.

Question 17

A photon with energy less than the work function of a metal strikes the surface. What happens?

Accepted Answer

No electron is emitted.

Question 18

Which of the following best explains why the photoelectric effect supports the particle model of light?

Accepted Answer

Electrons are emitted only above a threshold frequency, regardless of intensity.

Question 19

A beam of electrons and a beam of protons are shot through a double slit at the same speed. Which statement is true?

Accepted Answer

Both produce interference patterns, but the electron pattern has wider spacing.

Chapter 38: Quantization – Study Notes

Study Guide - Practice Questions

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