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IB · C · multiple choice

Wave behaviour · Question 2

Wave behaviour · Original GioPhysics question with a detailed, mark-by-mark answer guide.

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Marks
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Answer
Complete
multiple choice1 mark

A sound wave of frequency 256 Hz travels through air at 340 m s⁻¹ and then passes into water, where its speed is 1500 m s⁻¹. What are its frequency and wavelength in the water?

  1. A

    256 Hz and 1.33 m

  2. B

    256 Hz and 5.86 m

  3. C

    1130 Hz and 1.33 m

  4. D

    58 Hz and 5.86 m

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Answer overviewCorrect answer: B — 256 Hz and 5.86 m
01

Answer and reasoning

1 mark
How to approach it

Predict from the governing principle before looking for a matching option. Then reject alternatives by checking direction, units, limiting behaviour or the physical meaning of each statement.

  1. 1

    The correct choice is B: 256 Hz and 5.86 m

  2. 2

    The frequency is fixed by the source and does not change at a boundary, which eliminates C and D at once. The wavelength changes with the speed: 1500/256 = 5.86 m.

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