Physics 9702 · AS & A Level · The diffraction grating
The diffraction grating — practice question
Monochromatic light of a single frequency is incident normally on a diffraction grating. The resulting interference pattern of bright and dark fringes is produced on the semicircular screen shown in Fig. 6.1. The wavelength of the light is $520\,\text{nm}$. The spacing between adjacent lines in the grating is $3.8 \times 10^{-6}\,\text{m}$.
(a)[3]
Determine how many bright fringes are formed on the screen.
(b(i))[1]
The light is replaced with red light of a single frequency. State whether the frequency of the red light is greater than, less than or the same as the frequency of the original light.
(b(ii))[2]
State and explain the effect of this change on the number of bright fringes formed on the screen. No calculation is needed.
Worked solution & mark scheme
This 6-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Uses the relation $n\lambda = d\sin\theta$” …