IB Physics Topic 12.1

An electron of low energy is enclosed within a high potential barrier. What is the process by which the electron can escape?

• Quantum tunneling

• Energy–mass conversion

• Diffraction

• Barrier climbing

A beam of monochromatic radiation is made up of photons each of momentum p. The intensity of the beam is doubled without changing frequency. What is the momentum of each photon after the change?

• p/2

• p

• 2p

• 4p

Three observations of the behaviour of electrons are

I. electron emission as a result of the photoelectric effect

II. electron diffraction as an electron interacts with an atom

III. emission of radio waves as a result of electrons oscillating in a conductor.

Which observations are evidence that the electron behaves as a particle?

• I and II only

• I and III only

• II and III only

• I, II and III

A particle is confined within a nucleus. What is the order of magnitude of the uncertainty in the momentum of the particle?

• 10^–10 N s

• 10^–15 N s

• 10^–20 N s

• 10^–25 N s

When green light is incident on a clean zinc plate no photoelectrons are emitted. What change may cause the emission of photoelectrons?

• Using a metal plate with larger work function

• Changing the angle of incidence of the green light on the zinc plate

• Using shorter wavelength radiation

• Increasing the intensity of the green light

A photoelectric cell is connected in series with a battery of emf 2 V. Photons of energy 6 eV are incident on the cathode of the photoelectric cell. The work function of the surface of the cathode is 3 eV. What is the maximum kinetic energy of the photoelectrons that reach the anode?

• 1 eV

• 3 eV

• 5 eV

• 8 eV

Which of the following is evidence for the wave nature of the electron?

• Continuous energy spectrum in β– decay

• Electron diffraction from crystals

• Existence of atomic energy levels

• Existence of nuclear energy levels

Monochromatic electromagnetic radiation is incident on a metal surface. The kinetic energy of the electrons released from the metal

• is constant because the photons have a constant energy.

• is constant because the metal has a constant work function

• varies because the electrons are not equally bound to the metal lattice.

• varies because the work function of the metal is different for different electrons.

Different metal surfaces are investigated in an experiment on the photoelectric effect. A graph of the variation of the maximum kinetic energy of photoelectrons with the frequency of the incident light is drawn for each metal. Which statement is correct?

• All graphs have the same intercept on the frequency axis.

• The work function is the same for all surfaces.

• All graphs have the same slope.

• The threshold frequency is the same for all surfaces.

Photoelectrons are emitted at a certain rate when monochromatic light is incident on a metal surface. Light of the same intensity but of higher frequency is now used. After this change, the rate of emission of electrons from the surface is

• zero.

• lower

• the same

• higher