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CAIE A-Level Physics AS 8.4 The Diffraction Grating Questions

Practise using d sin θ = nλ to calculate grating order, wavelength and angle, and interpreting measured maxima in a diffraction experiment.

Syllabus
2028–2030
Course
Physics 9702
Level
AS

Exam points

  • calculate wavelength, order or angle from diffraction-grating maxima using d sin θ = nλ
  • describe a grating experiment and use measured orders, angles and grating spacing to determine light wavelength

Covered syllabus points

8.4.1—D sin θ = nλ8.4.2—The use of a diffraction grating to determine the wavelength of light

Question 1

[Maximum number: 1]

Light of wavelength 5.50×10−7 m5.50 \times 10^{-7} \mathrm{~m} from a laser is incident normally on a diffraction grating.
The diffracted light is incident on a semicircular screen, as shown in the view from above.

view from above

view from above

A total of 9 bright dots are formed on the screen.
The grating is at the centre of the semicircle. The lines of the grating are vertical. The separation between adjacent lines in the grating is d.

What is a possible value of d ?

A

2.25×10−6 m2.25 \times 10^{-6} \mathrm{~m}

B

2.80×10−6 m2.80 \times 10^{-6} \mathrm{~m}

C

4.40×10−6 m4.40 \times 10^{-6} \mathrm{~m}

D

4.95×10−6 m4.95 \times 10^{-6} \mathrm{~m}

Question 2

[Maximum number: 1]

Which property of a light wave can be determined using a diffraction grating?

A

amplitude

B

intensity

C

speed

D

wavelength

Question 3

[Maximum number: 1]

A diffraction grating with N lines per metre is used to diffract light of various wavelengths λ\lambda.
The graph shows the relation between the diffraction angle θ\theta and λ\lambda for different wavelengths in the nth n^{\text {th }} order interference pattern.

Figure for Question 3 — CAIE A-Level Physics AS

What is the gradient of the graph?

A

N n

B

Nn\frac{N}{n}

C

nN\frac{n}{N}

D

1Nn\frac{1}{N n}

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