Quantum Physics

Question 1

Define the work function

Answer 1

The work function of a material is defined as the minimum amount of work necessary to remove a free electron from the surface of the material.

Question 2

Define the threshold frequency

Answer 2

Threshold frequency is the minimum frequency of an incident radiation required to just remove an electron from the surface of a metal.

Question 3

Define the photoelectron

Answer 3

Photoelectron is used to indicate that the electron has been emitted when light falls on the surface of a metal.

Question 4

Define the photon

Answer 4

Packet/quantum/discrete amount of energy of electromagnetic radiation having energy equal to Planck constant × frequency

Question 5

What is the relationship between work function and threshold frequency?

Answer 5

∅ = hf₀

Question 6

How can the threshold p.d. of an LED be used to find photon energy?

Answer 6

The energy transferred by the electrons (e x V) is equal to the energy of the photons produced (hf).

Question 7

What is required for a photon to be able to produce photoelectrons? (Frequency description)

Answer 7

Its frequency is greater than the threshold frequency

Question 8

What is required for a photon to be able to produce photoelectrons? (energy description)

Answer 8

Its energy is greater than the work function

Question 9

How do photons and electrons interact?

Answer 9

A single photon can be absorbed/emitted by a single electron which gains/loses the energy of the photon.

Question 10

What effect does increasing the frequency of a monochromatic light source have on photoelectrons produced?

Answer 10

Photoelectrons will have a greater maximum kinetic energy.

Question 11

What is the effect of increasing the intensity of a monochromatic light source on photoelectrons produced?

Answer 11

More photoelectrons will be produced but they will have the same maximum kinetic energy

Question 12

Why does the kinetic energy of photoelectrons from monochromatic light vary in the photoelectric effect?

Answer 12

The work function is a minimum energy. Some electrons are liberated from deeper into the metal and require more energy to be liberated

Question 13

What two factors that determine the maximum kinetic energy of photoelectrons?

Answer 13

The frequency of the light and the work function of the metal

Question 14

What determines the rate at which energy is delivered by a wave?

Answer 14

Intensity/amplitude of the wave

Question 15

What is hf in Einstein’s photoelectric effect equation (hf = 𝜙 + KE(max))

Answer 15

The energy of the incident photon

Question 16

What is 𝜙 in Einstein’s photoelectric effect equation (hf = 𝜙 + KE(max))

Answer 16

The work function of the metal.

Question 17

What is KE(max) in Einstein’s photoelectric effect equation (hf = 𝜙 + KE(max))

Answer 17

The maximum kinetic energy of the photoelectrons

Question 18

According to the wave model how is energy transferred from light to electrons in a metal?

Answer 18

It is delivered continuously and builds up over time

Question 19

How do you calculate the energy of a photon?

Answer 19

E = hf OR E =hc/λ

Question 20

What is an electron volt?

Answer 20

The energy gained or lost by an electron passing through a potential difference of 1V

Question 21

How do convert from eV to J?

Answer 21

multiply by 1.6x10^-19

Question 22

How do convert from J to eV?

Answer 22

divide by 1.6x10^-19

Question 23

What is meant by wave particle duality?

Answer 23

It describes how all matter can display both wave and particle properties.

Question 24

What is the key piece of evidence for wave particle duality?

Answer 24

When an electron beam passes through polycrystaline graphite it produces a diffraction and interference pattern pattern+ Photoelectric effect

Question 25

How do you calculate the wavelength of a particle with mass?

Answer 25

λ=h/p=h/(mv)