Whenever a transverse wave, travelling in a rarer medium, encounters a denser medium:
Correct answer: C. An incident crest on reflection becomes a trough
- A. An incident crest on reflection disappears
- B. An incident trough on reflection remains a trough
- C. An incident crest on reflection becomes a trough
- D. An incident crest on reflection remains a crest
Explanation
When a transverse wave travels from a rarer medium to a denser medium, it reflects at the boundary. During this reflection, the wave undergoes a 180-degree phase shift, causing the crest of the incident wave to become a trough upon reflection. This phase inversion is characteristic of waves reflecting from a denser medium. In summary, Option C is correct as the incident crest indeed becomes a trough. Options A, B, and D are incorrect because they do not account for the phase inversion that occurs during reflection from a denser medium.
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About Waves
Progressive waves transfer energy through oscillations, with wavelength, frequency, amplitude and wave speed related by v = fλ; sound speed depends on the medium. Superposition produces interference and stationary waves in strings and organ pipes, while simple harmonic motion describes the oscillation itself and must be distinguished from wave propagation.
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