Fig. 1 shows water waves in a ripple tank moving towards a narrow gap in a barrier. A student uses a stroboscope to see the wave pattern clearly. The waves ...
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Fig. 1 shows water waves in a ripple tank moving towards a narrow gap in a barrier. A student uses a stroboscope to see the wave pattern clearly. The waves have frequency 5.0 Hz and wavelength 3.0 cm before reaching the gap.
(a) State the type of wave made on the water surface. [1]
(b) Describe how the student could measure the wavelength from the diagram or ripple tank pattern. [2]
(c) Explain why the waves spread out more if the width of the gap is reduced. [2]
(d) Calculate the speed of the water waves. [1]
Answer Details
(a) Water-surface waves are transverse waves. [1]
(b) Measure the distance across several complete gaps between equivalent wavefronts, then divide this total distance by the number of wavelengths measured. Measuring several wavelengths reduces percentage uncertainty. [2]
(c) A narrower gap has a width closer to the wavelength. Diffraction is greater when the gap size is comparable with the wavelength, so the waves spread out more. [2]
(d) Convert \(3.0\text{ cm}\) to \(0.030\text{ m}\): \[v=f\lambda=5.0\times0.030=0.15\text{ m/s}\] [1]
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