Physics 9702 · AS & A Level · The diffraction grating
The diffraction grating — practice question
A microphone, linked to a cathode-ray oscilloscope (CRO), picks up a sound wave. The trace shown on the CRO screen is given in Fig. 5.1. The CRO time-base setting is $2.0 \times 10^{-5}\,\text{s cm}^{-1}$.
(a(i))[2]
Determine the sound wave frequency.
(a(ii))[2]
The sound wave intensity is doubled. The frequency stays the same. Assume that the trace amplitude is proportional to the sound wave amplitude. On Fig. 5.1, sketch the updated trace on the screen.
(a(iii))[1]
The time-base has now been switched off. Describe the trace displayed on the screen.
(b(i))[2]
Calculate the wavelength of the light beam.
(b(ii))[2]
Determine the highest diffraction order of the beam from the grating.
Worked solution & mark scheme
This 9-mark question has a full step-by-step worked solution and mark scheme. One marking point: “$T = 2.0\times10^{-5} \times 6.0 = 1.2\times10^{-4}\,\text{s}$” …