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Lasers: WJEC A‑Level Physics questions

Every WJEC A-Level Physics exam question on 2.8 Lasers, 2016–2025, with its mark scheme and examiner’s report.

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1,173 questions

  1. Q6(b)(i)

    Summer 2025 · AS Unit 2

    3 marks2.8 Lasers
    The whole paper ↗
    Summer 2025 AS Unit 2, question 6(b)(i): Explain what is meant by stimulated emission. [3]

  2. Q9(a)(i)

    Summer 2024 · AS Unit 2

    2 marks2.8 Lasers
    The whole paper ↗
    Summer 2024 AS Unit 2, question 9(a)(i): Explain what is meant by stimulated emission involving levels U and G. [2]

  3. Q9(a)(ii)

    Summer 2024 · AS Unit 2

    1 mark2.8 Lasers
    The whole paper ↗
    Summer 2024 AS Unit 2, question 9(a)(ii): State why there must be more electrons in U than in G for light amplification to occur. [1]

  4. Q9(b)

    Summer 2024 · AS Unit 2

    3 marks2.8 Lasers
    The whole paper ↗
    Summer 2024 AS Unit 2, question 9(b): Calculate the wavelength of the light emitted by stimulated emission. [3]

  5. Q8(a)

    Summer 2023 · AS Unit 2

    3 marks2.8 Lasers
    The whole paper ↗
    Summer 2023 AS Unit 2, question 8(a): The laser transition between level U and level L produces stimulated photons of wavelength 1.06 × 10–6 m. Determine the value of energy level L in eV. [3]

  6. Q8(b)

    Summer 2023 · AS Unit 2

    2 marks2.8 Lasers
    The whole paper ↗
    Summer 2023 AS Unit 2, question 8(b): When explaining the operation of this laser, a student writes the following: Pumping is required to move electrons from ground level to level P which is a metas

  7. Q8(c)

    Summer 2023 · AS Unit 2

    2 marks2.8 Lasers
    The whole paper ↗
    Summer 2023 AS Unit 2, question 8(c): Semiconductor lasers are regularly used in DVD players and bar code scanners. State two advantages that these semiconductor lasers have over gas lasers. [2]

  8. Q8(d)

    Summer 2023 · AS Unit 2

    2 marks2.8 Lasers
    The whole paper ↗
    Summer 2023 AS Unit 2, question 8(d): As electronic technology advances, outdated electronic devices and their components are discarded. It has been estimated that 50 million tonnes of electronic wa

  9. Q7(a)(i)

    Summer 2022 · AS Unit 2

    1 mark2.8 Lasers
    The whole paper ↗
    Summer 2022 AS Unit 2, question 7(a)(i): The laser is pumped to create a population inversion between level U and level L. State what is meant by a population inversion for this laser. [1]

  10. Q7(a)(ii)

    Summer 2022 · AS Unit 2

    1 mark2.8 Lasers
    The whole paper ↗
    Summer 2022 AS Unit 2, question 7(a)(ii): Draw three arrows on the diagram to show the transitions required for this population inversion to be sustained. [1]

  11. Q7(a)(iii)

    Summer 2022 · AS Unit 2

    3 marks2.8 Lasers
    The whole paper ↗
    Summer 2022 AS Unit 2, question 7(a)(iii): Explain why a population inversion is needed for light amplification to take place. [3]

  12. Q7(b)

    Summer 2022 · AS Unit 2

    3 marks2.8 Lasers
    The whole paper ↗
    Summer 2022 AS Unit 2, question 7(b): Determine whether or not visible light will be produced by the lasing transition from level U to level L, giving your reasoning. [3]

  13. Q6(b)(i)

    Summer 2019 · AS Unit 2

    4 marks2.8 Lasers
    The whole paper ↗
    Summer 2019 AS Unit 2, question 6(b)(i): Referring to populations, explain the part played in the operation of the laser by: I. transition A; [2] II. transition D. [2]

  14. Q6(b)(ii)

    Summer 2019 · AS Unit 2

    4 marks2.8 Lasers
    The whole paper ↗
    Summer 2019 AS Unit 2, question 6(b)(ii): Calculate the wavelength of the radiation emitted by stimulated emission from the laser, and name the region of the electromagnetic spectrum in which it lies. [

  15. Q3(a)(i)

    Summer 2018 · AS Unit 2

    3 marks2.8 Lasers
    The whole paper ↗
    Summer 2018 AS Unit 2, question 3(a)(i): Calculate the wavelength of light emitted by stimulated emission. [3]

  16. Q3(a)(ii)

    Summer 2018 · AS Unit 2

    2 marks2.8 Lasers
    The whole paper ↗
    Summer 2018 AS Unit 2, question 3(a)(ii): Assuming that some photons of this wavelength are already present in the laser cavity, explain why a population inversion is needed for light amplification to t

  17. Q7(a)

    Summer 2017 · Unit 3

    5 marks2.8 Lasers
    The whole paper ↗
    Summer 2017 Unit 3, question 7(a): In your own words explain what a megamaser is and how it works. (See paragraphs 1, 4, 7 and 8.) [5]

  18. Q7(b)

    Summer 2017 · Unit 3

    3 marks2.8 Lasers
    The whole paper ↗
    Summer 2017 Unit 3, question 7(b): If the lifetime of a metastable level leading to visible light is 2 μs, estimate the lifetime of a 22.235 GHz maser transition. (See paragraph 2.) [3]

  19. Q8(a)(i)

    Summer 2017 · AS Unit 2

    2 marks2.8 Lasers
    The whole paper ↗
    Summer 2017 AS Unit 2, question 8(a)(i): Calculate the wavelength of photons which can take part in transitions between levels U and L. [2]

  20. Q8(a)(ii)

    Summer 2017 · AS Unit 2

    4 marks2.8 Lasers
    The whole paper ↗
    Summer 2017 AS Unit 2, question 8(a)(ii): Describe the processes of absorption and stimulated emission involving levels U and L. [4] absorption: stimulated emission:
All 26 questions on Lasers, as a list
  1. Summer 2025, AS Unit 2, Q6(b)(i) (3 marks): Explain what is meant by stimulated emission. [3]
  2. Summer 2024, AS Unit 2, Q9(a)(i) (2 marks): Explain what is meant by stimulated emission involving levels U and G. [2]
  3. Summer 2024, AS Unit 2, Q9(a)(ii) (1 mark): State why there must be more electrons in U than in G for light amplification to occur. [1]
  4. Summer 2024, AS Unit 2, Q9(b) (3 marks): Calculate the wavelength of the light emitted by stimulated emission. [3]
  5. Summer 2023, AS Unit 2, Q8(a) (3 marks): The laser transition between level U and level L produces stimulated photons of wavelength 1.06 × 10–6 m. Determine the value of energy level L in eV. [3]
  6. Summer 2023, AS Unit 2, Q8(b) (2 marks): When explaining the operation of this laser, a student writes the following: Pumping is required to move electrons from ground level to level P which is a metas
  7. Summer 2023, AS Unit 2, Q8(c) (2 marks): Semiconductor lasers are regularly used in DVD players and bar code scanners. State two advantages that these semiconductor lasers have over gas lasers. [2]
  8. Summer 2023, AS Unit 2, Q8(d) (2 marks): As electronic technology advances, outdated electronic devices and their components are discarded. It has been estimated that 50 million tonnes of electronic wa
  9. Summer 2022, AS Unit 2, Q7(a)(i) (1 mark): The laser is pumped to create a population inversion between level U and level L. State what is meant by a population inversion for this laser. [1]
  10. Summer 2022, AS Unit 2, Q7(a)(ii) (1 mark): Draw three arrows on the diagram to show the transitions required for this population inversion to be sustained. [1]
  11. Summer 2022, AS Unit 2, Q7(a)(iii) (3 marks): Explain why a population inversion is needed for light amplification to take place. [3]
  12. Summer 2022, AS Unit 2, Q7(b) (3 marks): Determine whether or not visible light will be produced by the lasing transition from level U to level L, giving your reasoning. [3]
  13. Summer 2019, AS Unit 2, Q6(b)(i) (4 marks): Referring to populations, explain the part played in the operation of the laser by: I. transition A; [2] II. transition D. [2]
  14. Summer 2019, AS Unit 2, Q6(b)(ii) (4 marks): Calculate the wavelength of the radiation emitted by stimulated emission from the laser, and name the region of the electromagnetic spectrum in which it lies. [
  15. Summer 2018, AS Unit 2, Q3(a)(i) (3 marks): Calculate the wavelength of light emitted by stimulated emission. [3]
  16. Summer 2018, AS Unit 2, Q3(a)(ii) (2 marks): Assuming that some photons of this wavelength are already present in the laser cavity, explain why a population inversion is needed for light amplification to t
  17. Summer 2017, Unit 3, Q7(a) (5 marks): In your own words explain what a megamaser is and how it works. (See paragraphs 1, 4, 7 and 8.) [5]
  18. Summer 2017, Unit 3, Q7(b) (3 marks): If the lifetime of a metastable level leading to visible light is 2 μs, estimate the lifetime of a 22.235 GHz maser transition. (See paragraph 2.) [3]
  19. Summer 2017, AS Unit 2, Q8(a)(i) (2 marks): Calculate the wavelength of photons which can take part in transitions between levels U and L. [2]
  20. Summer 2017, AS Unit 2, Q8(a)(ii) (4 marks): Describe the processes of absorption and stimulated emission involving levels U and L. [4] absorption: stimulated emission:
  21. Summer 2017, AS Unit 2, Q8(a)(iii) (1 mark): If the relative populations of levels P, U and L are 0.2%, 54.0% and 45.8%, state with a reason whether absorption or stimulated emission is the more likely eve
  22. Summer 2017, AS Unit 2, Q8(a)(iv) (2 marks): The laser is pumped by promoting electrons from the ground state to level P. Explain why electrons must spend only a very short time in level P, but a relativel
  23. Summer 2017, AS Unit 2, Q8(b) (4 marks): It has been suggested that energy should be carried across the country as high power light beams from lasers. Discuss whether or not this might be a good altern
  24. Summer 2016, AS Unit 2, Q1(a)(i) (3 marks): Calculate the wavelength of radiation emitted in the transition from level U to level L. [3]
  25. Summer 2016, AS Unit 2, Q1(a)(ii) (3 marks): Explain how stimulated emission enables amplification of infra-red radiation of this wavelength. [3]
  26. Summer 2016, AS Unit 2, Q1(b) (2 marks): Explain the advantage of a four-level laser system over a three-level system. [2]

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