Paper 2 Superposition of Waves Drills

Q1 Young double-slit fringes

A double-slit experiment uses slit separation $0.420\mathrm{mm}$ and screen distance $1.80\mathrm{m}$. The measured fringe spacing is $2.90\mathrm{mm}$.

1. State two conditions needed for a clear stationary fringe pattern. [2]
2. Calculate the wavelength of the light. [3]
3. State what happens to the fringe spacing if the screen is moved further away. [1]
4. Explain why bright and dark fringes form. [3]

Q2 Stationary wave on a string

A string fixed at both ends has length $0.900\mathrm{m}$. It vibrates in its third harmonic at frequency $180\mathrm{Hz}$.

1. State the number of loops in the third harmonic. [1]
2. Calculate the wavelength. [2]
3. Calculate the wave speed on the string. [2]
4. Explain why nodes remain at fixed positions. [2]

Q3 Diffraction grating

A grating has $600$ lines per millimetre. Monochromatic light of wavelength $520\mathrm{nm}$ is incident normally.

1. Calculate the grating spacing. [2]
2. Calculate the angle of the first-order maximum. [2]
3. Determine whether a third-order maximum is possible. [2]