P.3.2.2.1 The photoelectric effect

The graph shows how the maximum kinetic energy E_k of photoelectrons emitted from a metal surface varies with the reciprocal of the wavelength λ of the incident radiation.

What is the gradient of this graph?

• c

• h

• hc

• h/c

Photons of wavelength 290 nm are incident on a metal plate. The work function of the metal is 4.1 eV

What is the maximum kinetic energy of the emitted electrons?

• 0.19 eV

• 4.3 eV

• 6.9 eV

• 8.4 eV

Which statement suggests that electrons have wave properties?

• Electrons are emitted in photoelectric effect experiments.

• Electrons are released when atoms are ionised.

• Electrons produce dark rings in diffraction experiments.

• Electron transitions in atoms produce line spectra.

When light of a certain frequency greater than the threshold frequency of a metal is directed at the metal, photoelectrons are emitted from the surface. The power of the light incident on the metal surface is doubled.

Which row shows the effect on the maximum kinetic energy and the number of photoelectrons emitted per second?

• Maximum kinetic energy: remains unchanged

  Number of photoelectrons emitted per second: remains unchanged

• Maximum kinetic energy: doubles

  Number of photoelectrons emitted per second: remains unchanged

• Maximum kinetic energy: remains unchanged

  Number of photoelectrons emitted per second: doubles

• Maximum kinetic energy: doubles

  Number of photoelectrons emitted per second: doubles

Line X on the graphs below shows how the maximum kinetic energy of emitted photoelectrons varies with the frequency of incident radiation for a particular metal.

Which graph shows the results for a metal Y that has a higher work function than X?

• 
• 
• 
• 

A beam of light of wavelength λ is incident on a clean metal surface and photoelectrons are emitted. The wavelength of the light is halved but energy incident per second is kept the same.

Which row in the table is correct?

• Maximum kinetic energy of the emitted photoelectrons: Increases

  Number of photoelectrons emitted per second: Unchanged

• Maximum kinetic energy of the emitted photoelectrons: Decreases

  Number of photoelectrons emitted per second: Increases

• Maximum kinetic energy of the emitted photoelectrons: Increases

  Number of photoelectrons emitted per second: Decreases

• Maximum kinetic energy of the emitted photoelectrons: Decreases

  Number of photoelectrons emitted per second: Unchanged

In an experiment to demonstrate the photoelectric effect, a charged metal plate is illuminated with light from different sources. The plate loses its charge when an ultraviolet light source is used but not when a red light source is used.

What is the reason for this?

• The intensity of the red light is too low.

• The wavelength of the red light is too short.

• The frequency of the red light is too high.

• The energy of red light photons is too small.

Electromagnetic radiation incident on a metal surface can cause electrons to be emitted.

Which of the following statements is correct?

• Every photon incident on the surface causes an electron to be emitted.

• All the emitted electrons have the same energy.

• The range of energy of the emitted electrons depends on the intensity of the radiation.

• If the incident radiation is of a single frequency, the number of electrons emitted per second increases if the intensity of the radiation increases.

When comparing X-rays with UV radiation, which statement is correct?

• X-rays have a lower frequency.

• X-rays travel faster in a vacuum.

• X-rays do not show diffraction and interference effects.

• Using the same element, photoelectrons emitted using X-rays have the greater maximum kinetic energy.

Monochromatic radiation from a source of light (source A) is shone on to a metallic surface and electrons are emitted from the surface. When a second source (source B) is used no electrons are emitted from the metallic surface. Which property of the radiation from source A must be greater than that from source B?

• amplitude

• frequency

• intensity

• wavelength