Photons, the photoelectric effect and line spectra: Edexcel International A Level Physics questions

Every Edexcel International A Level Physics exam question on Photons, the photoelectric effect and line spectra (specification points 57–63), 2019–2025, with its mark scheme and examiner’s report.

All 97 questions on Photons, the photoelectric effect and line spectra, as a list

June 2025, AS Unit 2, Q5 (1 mark): An energy level diagram for the hydrogen atom is shown. Arrows A, B, C and D show four possible electron transitions. Energy / eV Not to scale 0 B C –0.85 –1.51
June 2025, AS Unit 2, Q9 (1 mark): When monochromatic light is incident on the surface of a metal, photoelectrons are emitted. Which of the following statements is correct? A The maximum kinetic
June 2025, AS Unit 2, Q18(a) (2 marks): One type of UV lamp contains mercury atoms in an evacuated glass tube. When a large potential difference is applied between two electrodes in the tube, electron
June 2025, AS Unit 2, Q18(b)(ii) (4 marks): Determine the number of photons incident on the glass screen in this time. wavelength of UV light = 395 nm (4) Number of photons =
June 2025, AS Unit 2, Q18(c) (2 marks): The potential difference applied between the electrodes in the UV lamp is increased. Explain the effect this would have on the frequency of the UV light produce
June 2025, AS Unit 2, Q18(d) (2 marks): Suggest why the hardening time of the glue is reduced if the UV lamp is moved closer to the mobile phone screen. (2)
January 2025, AS Unit 2, Q9 (1 mark): The diagram shows the energy needed for an electron in the ground state of a mercury atom to move to different energy levels. Not to scale 7.73 eV 6.70 eV 5.46
January 2025, AS Unit 2, Q19(a) (3 marks): A beam of monochromatic light is directed onto the metal plate and causes the photoelectric effect. All photons in the beam have the same energy. Explain why th
January 2025, AS Unit 2, Q19(b) (5 marks): The scientist connected the photocell to an ammeter and battery, as shown. A photocell 1.5 V Photoelectrons are attracted to the electrode, causing a current in
January 2025, AS Unit 2, Q19(c) (5 marks): The scientist reversed the connections to the battery, as shown. A photocell 1.5 V The battery has negligible internal resistance. When photoelectrons have enou
January 2025, Unit 5, Q18(a) (3 marks): Atoms in the outer regions of the Sun absorb electromagnetic radiation. This produces the dark lines in the spectrum. Explain why electromagnetic radiation is o
October 2024, AS Unit 2, Q2 (1 mark): Light from a discharge tube is viewed through a diffraction grating. An emission line spectrum is observed. Which of the following explains how electrons in the
October 2024, AS Unit 2, Q19(a) (2 marks): Describe the photoelectric effect. (2)
October 2024, AS Unit 2, Q19(b) (2 marks): The photomultiplier can only detect electromagnetic radiation that causes the photoelectric effect. Explain why the photomultiplier cannot detect some frequenci
October 2024, AS Unit 2, Q19(c) (4 marks): Visible light has a range of wavelengths from 380 nm to 700 nm. The work function of the material used to make the photocathode is 1.48 eV. Deduce whether the p
June 2024, AS Unit 2, Q6 (1 mark): Which of the following describes threshold frequency? A The frequency of light that causes photoelectrons to have maximum kinetic energy. B The frequency of l
June 2024, AS Unit 2, Q10 (1 mark): Light of wavelength λ travelling at speed c is incident on a metal surface. Photoelectrons are emitted from the surface with a maximum kinetic energy 1 2 mvmax.
June 2024, AS Unit 2, Q17(a)(i) (2 marks): One of the emitted photons has an energy of 3.44 × 10 Calculate the frequency of this photon. (2) Frequency of photon =
June 2024, AS Unit 2, Q17(a)(ii) (6 marks): The electrical circuit applies a large potential difference (p.d.) across the discharge tube. Explain how the p.d. across the discharge tube causes photons to b
June 2024, AS Unit 2, Q17(b)(i) (3 marks): Show that the maximum speed of the emitted electrons is about 5.3 × 10 5 m s –1. work function of metal = 6.30 × 10 –19 J (3)
June 2024, AS Unit 2, Q18(c)(ii) (5 marks): Light incident on the sensor causes a current in a circuit in the camera. Light with a power of 1.0 W is incident on the sensor. The graph shows the relationshi
January 2024, AS Unit 2, Q4 (1 mark): Which of the following describes a change in energy of 1 eV? A A charge of 1 C is accelerated across a potential difference of 1 V. B A charge of 1 C passes a p
January 2024, AS Unit 2, Q10 (1 mark): In an atom, an electron drops from energy level E2 to energy level E1, as shown. E2 E1 A photon of wavelength λ is emitted. Which of the following expressions g
January 2024, AS Unit 2, Q19(a) (3 marks): The work function of layer 1 is 1.86 eV. Calculate the minimum frequency of light needed to release an electron from layer 1. (3) Minimum frequency =
January 2024, AS Unit 2, Q19(b) (5 marks): Light from the Sun is incident on the solar cell. The intensity of the incident light is constant. Layer 1 has a greater work function than layer 2. Photons not
January 2024, Unit 4, Q19(a) (3 marks): Collisions between electrons and oxygen atoms cause the emission of green light. Calculate the velocity of electrons that would cause green light of wavelength
October 2023, AS Unit 2, Q9 (1 mark): The diagram shows some of the energy levels for a hydrogen atom. –19 J Energy / × 10 0 –1.36 –2.42 –5.42 Which of the following expressions is equal to the lowe
October 2023, AS Unit 2, Q17(a) (6 marks): Explain these observations. (6)
October 2023, AS Unit 2, Q17(b)(i) (3 marks): The students replaced their original lamp with an ultraviolet lamp with a much greater intensity. Explain the effect this had on their experiment. (3)
October 2023, AS Unit 2, Q17(b)(ii) (4 marks): The ultraviolet lamp was replaced by a laser which emitted red light of wavelength 633 nm. Deduce whether the photoelectric effect will occur. work function of
October 2023, AS Unit 3, Q4(a)(i) (6 marks): Plot a graph of Emax on the y-axis against 1/λ on the x-axis on the grid opposite. Use the additional column of the table for your processed data. (6)
October 2023, AS Unit 3, Q4(a)(ii) (2 marks): The relationship between the maximum kinetic energy Emax of the emitted electrons and the wavelength λ of the incident photons is given by the equation hc λ = ϕ
October 2023, AS Unit 3, Q4(a)(iii) (4 marks): Determine a value of h. (4) h =
October 2023, AS Unit 3, Q4(a)(iv) (2 marks): Calculate the percentage difference between h and the accepted value for the Planck constant. (2) Percentage difference =
October 2023, AS Unit 3, Q4(b) (4 marks): The student’s investigation involves a small random error and a large systematic error. For each of these, suggest a source of the error and a realistic modific
June 2023, AS Unit 2, Q17(a) (2 marks): A photon interacts with this electron. Explain why this interaction causes the emission of another photon. (2)
June 2023, AS Unit 2, Q17(b)(i) (4 marks): Determine the energy, in eV, of this photon. (4) Photon energy = eV
June 2023, AS Unit 2, Q17(b)(ii) (2 marks): Explain whether the atom of hydrogen could emit a photon with this energy. (2)
June 2023, AS Unit 2, Q17(c)(i) (3 marks): Calculate the maximum possible speed of the electrons. work function = 5.89 × 10 −19 J (3) Maximum possible speed of the electrons =
June 2023, AS Unit 2, Q17(c)(ii) (3 marks): Explain why the photoelectric effect demonstrates light behaving as a particle, rather than a wave. (3)
June 2023, AS Unit 3, Q2(c) (2 marks): Solar cells are used as a source of electrical power. Describe two advantages of using solar cells to power a small water pump in a garden. (2)
January 2023, AS Unit 2, Q7 (1 mark): The diagram shows some of the energy levels in an atom. n = 3 n = 2 n = 1 (ground state) Electrons in this atom are excited from the ground state to the energy
January 2023, AS Unit 2, Q18(a)(i) (3 marks): Photoelectrons are released from the plate with a maximum speed of 3.51 × 10 5 m s –1. Calculate the energy of these photoelectrons in eV. (3) Energy = eV
January 2023, AS Unit 2, Q18(a)(ii) (4 marks): The table shows typical values of work function for four different metals. Metal Work function / 10 –19 J Magnesium 5.89 Aluminium 6.53 Zinc 6.88 Iron 7.20 The
January 2023, AS Unit 2, Q18(b) (4 marks): Photoelectrons are only emitted from a given metal surface if the frequency of the incident radiation is above a particular value. Explain why. (4)
January 2023, AS Unit 2, Q18(c) (2 marks): A student makes the following statement. ‘It does not matter what the value of the work function is for a particular metal. Photoelectrons can always be release
October 2022, AS Unit 2, Q2 (1 mark): The diagram shows four possible transitions of electrons in an atom. A D B C ground state Which of the transitions will result in the emission of a photon with
October 2022, AS Unit 2, Q14(a) (3 marks): Explain why the maximum kinetic energy of a released electron is less than the energy of each photon of light incident on the surface. (3)
October 2022, AS Unit 2, Q14(b) (4 marks): The frequencies of three different sources of light, A, B and C, are shown in the table below. Light source Frequency / 1015 Hz A 1.11 B 1.23 C 1.34 The light f
October 2022, AS Unit 2, Q17(a)(ii) (4 marks): Calculate the number of photons emitted by the LED in one minute. (4) Number of photons emitted in one minute =
October 2022, AS Unit 2, Q17(b) (2 marks): The red LED was replaced with a green LED which emits light with a shorter wavelength than the red LED. The current in the circuit did not change. Explain how r
June 2022, AS Unit 2, Q7 (1 mark): The diagram shows an electron transition between two energy levels in a hydrogen atom. –3.4 eV –13.6 eV Which of the following could not have caused this transi
June 2022, AS Unit 2, Q17(a) (1 mark): State what is meant by work function. (1)
June 2022, AS Unit 2, Q17(b) (6 marks): The ultraviolet (UV) section of the electromagnetic spectrum can be split into three parts, known as UVA, UVB and UVC. The range of wavelengths of these parts i
June 2022, AS Unit 2, Q17(c) (4 marks): A student used a zinc plate and UV light of different frequencies in an experiment. The student’s graph of maximum kinetic energy of the released electrons agai
June 2022, Unit 6, Q3(a) (2 marks): The relationship between the atomic number Z and the frequency f of the most intense spectral line is given by Z = k f n where k and n are constants. Explain wh
January 2022, AS Unit 2, Q13 (6 marks): * 13 In the early 20th century, observations of the photoelectric effect demonstrated that light behaves as a particle. Explain how observations from the photoe
January 2022, AS Unit 2, Q18(a) (4 marks): When light from Sirius A passes through the hydrogen in the outer layers of the star, some light is absorbed. This causes electrons in the hydrogen to be excite
January 2022, AS Unit 2, Q18(c) (2 marks): When hydrogen gas is excited in the laboratory, only certain wavelengths of light are emitted. Explain why. (2)
October 2021, AS Unit 2, Q14(a) (2 marks): Explain why this observation cannot be explained by the wave model of electromagnetic radiation. (2)
October 2021, AS Unit 2, Q14(b)(i) (4 marks): Calculate the maximum speed with which electrons are released from the plate. work function of zinc = 4.3 eV (4) Maximum speed of electrons =
October 2021, AS Unit 2, Q14(b)(ii) (3 marks): A student suggests that a greater maximum speed of electrons could have been achieved if both: – a metal with a lower work function than zinc was used – ultravi
October 2021, AS Unit 2, Q16(a) (6 marks): Explain the process that results in the emission of different wavelengths of visible light. Your answer should include reference to energy levels in atoms. (6)
October 2021, AS Unit 2, Q16(b) (2 marks): It is also possible to make the atoms in a sample of air emit visible light. Explain why the light emitted by the air has a large number of different wavelength
October 2021, AS Unit 2, Q18(b) (3 marks): The laser emits light with a wavelength of 532 nm. Calculate the energy, in J, of each photon. (3) Energy of photon = J
October 2021, AS Unit 2, Q18(c)(ii) (1 mark): When photons arriving at the satellite are detected, only those with a wavelength of exactly 532 nm are used in the analysis of the results. Suggest why. (1)
June 2021, AS Unit 2, Q8 (1 mark): The diagram shows some of the energy levels of a hydrogen atom. –0.54 eV –0.85 eV –1.51 eV –3.40 eV –13.60 eV An excited electron in the level –0.54 eV drops to
June 2021, AS Unit 2, Q15(a) (4 marks): The radiation from B has a wavelength of 280 nm. Show that this radiation has a photon energy of about 4.4 eV. (4)
June 2021, AS Unit 2, Q15(b) (6 marks): The student used the two sources of radiation to investigate the photoelectric effect for two different metals, copper and zinc. The following statements were m
June 2021, AS Unit 3, Q4(a) (3 marks): Explain why a graph of Va against 1/λ should give a straight line. (3)
June 2021, AS Unit 3, Q4(b)(i) (2 marks): Complete the table with the corresponding values of 1/λ. (2)
June 2021, AS Unit 3, Q4(b)(ii) (5 marks): Plot a graph of Va on the y-axis against 1/λ on the x-axis. (5)
June 2021, AS Unit 3, Q4(b)(iii) (3 marks): Determine the value of the Planck constant given by the student’s data. (3) Planck constant =
June 2021, AS Unit 3, Q4(b)(iv) (2 marks): The student states that the value for the Planck constant obtained from the graph is accurate. Evaluate the student’s statement. (2)
June 2021, AS Unit 3, Q4(c) (4 marks): Each LED in the investigation emits a narrow range of wavelengths. The wavelength value stated by the manufacturer is the wavelength of light that is emitted wi
June 2021, Unit 5, Q18(e) (6 marks): Ultraviolet radiation (UV) is produced when alpha particles interact with air. This can be used to detect alpha particles when a nuclear reactor is decommission
January 2021, AS Unit 2, Q4 (1 mark): Electromagnetic radiation can be described in terms of a photon model. Which of the following demonstrates the photon model of light? A diffraction patterns B H
January 2021, AS Unit 2, Q14 (4 marks): The diagram shows some of the energy levels for an atom of hydrogen. 0 eV − 0.85 eV − 1.5 eV − 3.4 eV − 13.6 eV When an electron with a kinetic energy of 12.3 e
January 2021, AS Unit 2, Q17(a) (5 marks): Calculate the maximum speed of the electrons as they are released from the metal surface. (5) Maximum speed =
January 2021, AS Unit 2, Q17(b) (4 marks): A student suggests that if the wavelength and intensity of the light used are both increased, the maximum speed of the electrons released from the metal surface
January 2021, AS Unit 2, Q20(b) (3 marks): It is suggested that the energy per photon could be important in determining if the radiation emitted by the smart meter is dangerous. The smart meter transmits
October 2020, AS Unit 2, Q14(a) (1 mark): State what is meant by work function. (1)
October 2020, AS Unit 2, Q14(b) (3 marks): When light with a frequency of 6.32 × 1015 Hz is incident on a metal, photoelectrons are released with a maximum kinetic energy of 3.60 × 10−18 J. Determine whi
October 2020, AS Unit 2, Q14(c)(i) (3 marks): Calculate the time taken for a potassium atom to absorb enough energy to release an electron. intensity of ultraviolet radiation = 38.0 mW m−2 area over which a
October 2020, AS Unit 2, Q14(c)(ii) (2 marks): In practice, electrons are emitted from the plate as soon as the ultraviolet radiation is incident on the plate. Explain how this provides evidence for the part
October 2020, AS Unit 2, Q15(a) (3 marks): Calculate E for a hydrogen atom, in eV. (3) E = eV
January 2020, AS Unit 2, Q6 (1 mark): When the photoelectric effect occurs, light incident on the surface of a metal releases electrons. Which of the following is an experimental observation of the
January 2020, AS Unit 2, Q12(b) (2 marks): Sand storms are common in the Sahara Desert. Explain why sand storms reduce the power generated by the solar panels. (2)
January 2020, AS Unit 2, Q14(a) (1 mark): State what is meant by the work function of a metal. (1)
January 2020, AS Unit 2, Q14(b) (2 marks): This photocell works with ultraviolet light but does not work with visible light. Explain why. (2)
January 2020, AS Unit 2, Q14(c)(i) (3 marks): The variable power supply was initially set at 0 V and the reading on the ammeter was 2.4 μA. The intensity of the ultraviolet light was then increased without
January 2020, AS Unit 2, Q14(c)(ii) (4 marks): The variable power supply was adjusted until the reading on the ammeter became 0 μA. The reading on the voltmeter was 3.59 V. Calculate the work function, in jo
January 2020, AS Unit 2, Q18(c)(i) (4 marks): Explain the process by which nitrogen atoms produce a line spectrum. (4)
January 2020, AS Unit 2, Q18(c)(ii) (1 mark): State why the line spectrum produced by oxygen atoms in the air would be different from the line spectrum produced by nitrogen atoms. (1)
June 2019, AS Unit 2, Q14 (6 marks): *14 In 1921, Albert Einstein was awarded the Nobel Prize for Physics “for his discovery of the law of the photoelectric effect”. To explain this effect, Einstei
June 2019, AS Unit 2, Q16(a) (3 marks): Describe the process by which visible light is emitted from the sodium atoms. (3)
June 2019, AS Unit 2, Q16(b) (3 marks): Calculate the energy, in eV, of a photon of visible light with a wavelength of 589 nm. (3) Photon energy = eV

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