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JAMB Physics 1985 Question 28

Question 28

Sound

When a sound wave passes from air into water its

  1. A.speed and frequency increase but its wavelength remains the same
  2. B.speed and wavelength increase but its frequency remains the same
  3. C.speed decreases
  4. D.speed remains the same but its frequency and wavelength change
  5. E.speed increases but its frequency and wavelength decrease.
Show the answer and explanation

Answer: B (speed and wavelength increase but its frequency remains the same)

Explanation

Frequency is set by the source and does not change. Sound is faster in water, so λ = v/f gets longer too.