Modern Physics

Light of a single wavelength is incident on a metal.  Electrons are released. The intensity of the light is then increased.
Which of the following changes occur?

• Rate of electron emission: increase.
  Energy of electrons: increase.
• Rate of electron emission: decrease.
  Energy of electrons: no change.
• Rate of electron emission: decrease.
  Energy of electrons: increase.
• Rate of electron emission: increase.
  Energy of electrons: no change.

The photoelectric effect only occurs if the light shining on the metal is:

• coherent.
• above a minimum intensity.
• above a minimum frequency.
• above a minimum wavelength.

The graph shows maximum kinetic energy of emitted electrons against frequency of incident light for a number of different metals.
The threshold frequency is determined by:

• the x-intercept.
• the y-intercept.
• the gradient.
• the area under the graph.

Tags

NGSS.HS-PS4-3

The following observations are made about the photoelectric effect:
1.   No electrons are emitted below the threshold frequency.
2.   Above the threshold frequency the energy of electrons depends on the frequency of the light.
3.   Increasing intensity increases the number of emitted electrons.
Which (if any) of these observations can be explained by a wave theory of light?

• All of them.
• 1 and 2 only.
• 3 only.
• None of them.

The photoelectric effect is when:

• Electrons collide inside a metal to release photons.
• One incident metal electron releases one photon.
• One incident photon releases one electron from a metal.
• Photons are absorbed in to metal ions releasing electrons.

The diagram shows a circuit involving a photoelectric cell. When UV light is shone onto the metal cathode, electrons are emitted establishing a photocurrent.
Which of the following changes could cause the photocurrent to stop?

• Increasing the potential difference of the power supply.
• Increasing the frequency of the UV light.
• Increasing the intensity of the UV light.
• Changing the metal surface to one with a smaller work function.