If the waves interfere constructively, the amplitude of the resulting wave would be:
Correct answer: B. Greater than either of the individual waves
- A. Less than either of the individual waves
- B. Greater than either of the individual waves
- C. Equal to the shortest of the individual waves
- D. Equal to the greatest of the individual waves
Explanation
Option A: The amplitude of the resulting wave can never be less than either of the individual waves. This is because the crests of the two waves cannot cancel each other out completely. Even if the two waves are out of phase by 180 degrees, the troughs of the two waves will still add together to form a wave with some amplitude. Option B: The amplitude of the resulting wave would be greater than either of the individual waves. When two waves interfere constructively, the crests of the two waves line up, resulting in a wave with an amplitude that is equal to the sum of the amplitudes of the two individual waves. For example, if two waves with amplitudes of 1 cm and 2 cm interfere constructively, the amplitude of the resulting wave will be 3 cm. Option C: The amplitude of the resulting wave can also never be equal to the shortest of the individual waves. This is because the crests of the two waves cannot be perfectly aligned if the waves have different amplitudes. Option D: The amplitude of the resulting wave can be equal to the greatest of the individual waves. This happens when the two waves have the same amplitude and are in phase.
This question appeared on the NUMS 2018 paper, which you can sit online with every answer explained.
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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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