Lesson 5.5.2

5.5.2 Diffraction gratings and the wavelength of light Quiz: Pearson Edexcel Physics, Unit 5

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 5.5.2, Diffraction gratings and the wavelength of light: 20 multiple choice questions for the Pearson Edexcel Physics (9PH0), Unit 5: Waves and Particle Nature of Light, written with Revision Ninja.

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The 20 questions

  1. What is the diffraction grating equation for maxima?

    • n lambda = d sin(theta)
    • n d = lambda sin(theta)
    • lambda = n d sin(theta)
    • n lambda = d tan(theta)

  2. In the grating equation, what does d represent?

    • The width of each slit
    • The number of slits per metre
    • The distance from the grating to the screen
    • The spacing between adjacent slits

  3. A grating has 500 lines per millimetre. What is the slit spacing d?

    • 5.0 micrometres
    • 0.5 micrometres
    • 20 micrometres
    • 2.0 micrometres

  4. Where does the zero-order maximum (n = 0) appear on the screen?

    • Straight through the grating, at theta = 0, with all wavelengths overlapping to give white light
    • At 90 degrees to the grating
    • Only for red light
    • As a dark fringe

  5. Compared with a double slit of the same spacing, what does a diffraction grating produce?

    • Wider maxima with lower peak intensity
    • Sharper and narrower bright maxima
    • Fewer orders of maxima
    • No maxima at all

  6. What limits the highest order n that can be observed with a grating?

    • The condition that sin(theta) cannot exceed 1, so n must be less than d/lambda
    • The width of the grating only
    • The wavelength alone, regardless of spacing
    • The number of lines on the grating alone

  7. When white light passes through a grating, which colour is deviated the most in each order?

    • Violet
    • Green
    • Red
    • Yellow

  8. A grating has slit spacing 2.0 micrometres. Light of wavelength 500 nm is used. What is the angle of the first-order maximum?

    • 30.0 degrees
    • 7.2 degrees
    • 25.0 degrees
    • 14.5 degrees

  9. A diffraction grating with spacing 2.0 micrometres gives a second-order maximum at 36.9 degrees. What is the wavelength of the light?

    • 300 nm
    • 1200 nm
    • 450 nm
    • 600 nm

  10. A grating has spacing 1.0 micrometre and light of wavelength 650 nm is used. Which orders are observed?

    • Only the first order, since d/lambda is about 1.5
    • No orders, since d is less than the wavelength
    • Orders up to the third, since d/lambda is about 3
    • Only the second order, since d/lambda is about 1.5

  11. Light of wavelength 600 nm produces a first-order maximum at 30 degrees from a grating. What is the number of lines per millimetre of the grating?

    • About 1200 lines per mm
    • About 83 lines per mm
    • About 830 lines per mm
    • About 500 lines per mm

  12. A grating has slit spacing 2.5 micrometres. For light of wavelength 500 nm, what is the angle of the second-order maximum?

    • 36.9 degrees
    • 11.5 degrees
    • 53.1 degrees
    • 23.6 degrees

  13. A first-order maximum appears at 19.5 degrees from a grating of spacing 2.0 micrometres. What is the wavelength of the light?

    • 1000 nm
    • 340 nm
    • 670 nm
    • 520 nm

  14. A grating has 300 lines per millimetre. What is its slit spacing?

    • 3.3 micrometres
    • 300 micrometres
    • 0.30 micrometres
    • 33 micrometres

  15. A grating has spacing 3.0 micrometres. Light of wavelength 600 nm is used. What is the angle of the third-order maximum?

    • 18.4 degrees
    • 65.4 degrees
    • 53.1 degrees
    • 36.9 degrees

  16. A student says that for a given grating, the angle of each maximum increases with wavelength. Which evaluation is correct?

    • Correct, because for a given order sin(theta) is proportional to lambda
    • Incorrect, because angles depend only on the number of slits
    • Correct, but only for the zero-order maximum
    • Incorrect, because longer wavelengths give smaller angles

  17. A grating's first-order maximum for light of wavelength 633 nm appears at 25.0 degrees. What is the slit spacing?

    • 0.67 micrometres
    • 2.5 micrometres
    • 1.5 micrometres
    • 3.5 micrometres

  18. A grating of spacing 2.0 micrometres is used with white light. What is the approximate angular separation of the first-order maxima for 400 nm and 700 nm light?

    • About 17 degrees
    • About 4.5 degrees
    • About 9.0 degrees
    • About 12 degrees

  19. Why does a diffraction grating give sharper maxima than a double slit of the same spacing?

    • Many slits interfere together, so the bright maxima become narrower while the intensity between them falls
    • The grating has fewer slits, so less interference occurs
    • Each slit is wider, so the maxima are sharper
    • The grating absorbs light between the maxima only

  20. A student says that the central maximum of a grating pattern in white light is white, and so is every higher order. Which evaluation is correct?

    • Correct, because every order is white
    • Correct, because higher orders overlap to form white light
    • Incorrect, because the central maximum is coloured
    • Incorrect for higher orders, which spread into a spectrum; only the zero-order maximum stays white

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