22.2. Photoelectric effect
A subsection of Physics, 9702, through 22. Quantum physics
Listing 10 of 46 questions
With reference to the photoelectric effect, state what is meant by the threshold frequency. Electromagnetic radiation of wavelength λ is incident on a metal surface. Electrons of maximum kinetic energy EMAX are emitted. On , sketch the variation with 1/λ of EMAX. EMAX 1 /h State an equation relating the gradient of the graph drawn on to the Planck constant h. Explain any symbols you use. Explain why, for any particular wavelength of electromagnetic radiation, most of the electrons are emitted with kinetic energies less than the maximum value EMAX. Light of a particular wavelength is incident on a metal surface and gives rise to a photoelectric current. The wavelength is reduced. The intensity of the light is kept constant. State and explain the effect, if any, on the photoelectric current.
9702_m16_qp_42
THEORY
2016
Paper 4, Variant 2
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By reference to the photoelectric effect, explain what is meant by work function energy. In an experiment, electromagnetic radiation of frequency f is incident on a metal surface. The results in show the variation with frequency f of the maximum kinetic energy EMAX of electrons emitted from the surface. EMAX /10–19 J 0.8 1.0 0.6 0.4 0.2 1.2 1.4 5.0 f / 1014 Hz 5.5 6.0 6.5 7.0 7.5 Determine the work function energy in J of the metal used in the experiment. work function energy = J The work function energy in eV for some metals is given in Table 10.1. Table 10.1 metal work function / eV tungsten magnesium potassium 4.49 3.68 2.26 Determine the metal used in the experiment. Show your working. The intensity of the electromagnetic radiation for one particular frequency in is increased. State and explain the change, if any, in: the maximum kinetic energy of the emitted electrons the rate of emission of photoelectrons.
9702_m20_qp_42
THEORY
2020
Paper 4, Variant 2
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Experiments are conducted to investigate the photoelectric effect. It is found that, on exposure of a metal surface to light, either electrons are emitted immediately or they are not emitted at all. Suggest why this observation does not support a wave theory of light. Data for the wavelength λ of the radiation incident on the metal surface and the maximum kinetic energy EK of the emitted electrons are shown in . λ / nm EK / 10–19 J – 4.44 Without any calculation, suggest why no value is given for EK for radiation of wavelength 650 nm. Use data from to determine the work function energy of the surface. work function energy = J Radiation of wavelength 240 nm gives rise to a maximum photoelectric current I. The intensity of the incident radiation is maintained constant and the wavelength is now reduced. State and explain the effect of this change on the maximum kinetic energy of the photoelectrons, the maximum photoelectric current I.
9702_s11_qp_41
THEORY
2011
Paper 4, Variant 1
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The photoelectric effect may be represented by the equation photon energy = work function energy + maximum kinetic energy of electron. State what is meant by work function energy. The variation with frequency f of the maximum kinetic energy EK of photoelectrons emitted from the surface of sodium metal is shown in . 6.0 6.5 7.0 7.5 8.0 4.5 5.0 5.5 0.2 0.4 0.6 0.8 EK / eV f / 1014 Hz Use the gradient of the graph of to determine a value for the Planck constant h. Show your working. h = J s The sodium metal in has a work function energy of 2.4 eV. The sodium is replaced by calcium which has a work function energy of 2.9 eV. On , draw a line to show the variation with frequency f of the maximum kinetic energy EK of photoelectrons emitted from the surface of calcium.
9702_s12_qp_42
THEORY
2012
Paper 4, Variant 2
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Some data for the work function energy Φ and the threshold frequency f0 of some metal surfaces are given in . metal Φ / 10–19 J f0 / 1014 Hz sodium zinc platinum 3.8 5.8 9.0 5.8 8.8 State what is meant by the threshold frequency. Calculate the threshold frequency for platinum. threshold frequency = Hz Electromagnetic radiation having a continuous spectrum of wavelengths between 300 nm and 600 nm is incident, in turn, on each of the metals listed in . Determine which metals, if any, will give rise to the emission of electrons. When light of a particular intensity and frequency is incident on a metal surface, electrons are emitted. State and explain the effect, if any, on the rate of emission of electrons from this surface for light of the same intensity and higher frequency.
9702_s13_qp_41
THEORY
2013
Paper 4, Variant 1
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Some data for the work function energy Φ and the threshold frequency f0 of some metal surfaces are given in . metal Φ / 10–19 J f0 / 1014 Hz sodium zinc platinum 3.8 5.8 9.0 5.8 8.8 State what is meant by the threshold frequency. Calculate the threshold frequency for platinum. threshold frequency = Hz Electromagnetic radiation having a continuous spectrum of wavelengths between 300 nm and 600 nm is incident, in turn, on each of the metals listed in . Determine which metals, if any, will give rise to the emission of electrons. When light of a particular intensity and frequency is incident on a metal surface, electrons are emitted. State and explain the effect, if any, on the rate of emission of electrons from this surface for light of the same intensity and higher frequency.
9702_s13_qp_43
THEORY
2013
Paper 4, Variant 3
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For a particular metal surface, it is observed that there is a minimum frequency of light below which photoelectric emission does not occur. This observation provides evidence for a particulate nature of electromagnetic radiation. State three further observations from photoelectric emission that provide evidence for a particulate nature of electromagnetic radiation. 1. 2. 3. Some data for the variation with frequency f of the maximum kinetic energy EMAX of electrons emitted from a metal surface are shown in . 5.5 6.0 6.5 7.0 7.5 0.2 0.4 0.6 0.1 0.3 0.5 E MAX / eV f / 1014 Hz Explain why emitted electrons may have kinetic energy less than the maximum at any particular frequency. Use to determine 1. the threshold frequency, threshold frequency = Hz 2. the work function energy, in eV, of the metal surface. work function energy = eV
9702_s14_qp_41
THEORY
2014
Paper 4, Variant 1
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For a particular metal surface, it is observed that there is a minimum frequency of light below which photoelectric emission does not occur. This observation provides evidence for a particulate nature of electromagnetic radiation. State three further observations from photoelectric emission that provide evidence for a particulate nature of electromagnetic radiation. 1. 2. 3. Some data for the variation with frequency f of the maximum kinetic energy EMAX of electrons emitted from a metal surface are shown in . 5.5 6.0 6.5 7.0 7.5 0.2 0.4 0.6 0.1 0.3 0.5 E MAX / eV f / 1014 Hz Explain why emitted electrons may have kinetic energy less than the maximum at any particular frequency. Use to determine 1. the threshold frequency, threshold frequency = Hz 2. the work function energy, in eV, of the metal surface. work function energy = eV
9702_s14_qp_43
THEORY
2014
Paper 4, Variant 3
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Briefly describe two phenomena associated with the photoelectric effect that cannot be explained using a wave theory of light. 1. 2. The maximum energy EMAX of electrons emitted from a metal surface when illuminated by light of wavelength λ is given by the expression EMAX = hc ( λ – 1 λ0) where h is the Planck constant and c is the speed of light. Identify the symbol λ0. The variation with 1 λ of EMAX for the metal surface is shown in . / 106 m–1 λ 1.5 2.0 2.5 3.0 3.5 4.0 EMAX / 10–19 J 1. Use to determine the magnitude of λ0. λ0 = m 2. Use the gradient of to determine a value for the Planck constant h. h = J s The metal surface in becomes oxidised. Photoelectric emission is still observed but the work function energy is increased. On , draw a line to show the variation with 1 λ of EMAX for the oxidised surface.
9702_s17_qp_42
THEORY
2017
Paper 4, Variant 2
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Questions Discovered
46