CAIE IGCSE Physics Wavelength and Gap Diffraction

Practise predicting and drawing diffraction from the wavelength-to-gap ratio, comparing semicircular spreading with nearly straight transmitted wavefronts.

Exam points

predict greatest spreading when wavelength is comparable to or larger than the gap width
predict less diffraction for a wider gap or a shorter wavelength at fixed gap size
draw transmitted fronts with unchanged spacing but curvature set by the gap ratio

[Maximum number: 4]

A loudspeaker produces a sound wave in air. The distance between the centre of a compression and the centre of a neighbouring rarefaction is 0.10 m .

Another loudspeaker produces a sound of wavelength 0.40 m . Sound from the loudspeaker reaches a sound absorbing surface with a gap of width 0.80 m at the centre.

Fig. 5.1 shows the arrangement.

Fig. 5.1

Explain whether it is possible to detect sound from the loudspeaker at either point J or at point K.
point J
point K

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3.1.9—Wavelength and gap size affects question 1