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JAMB Physics 1997 Question 32

Question 32

Sound

If the load at the end of a sonometer wire is immersed in a bucket of water, the original fundamental frequency of the wire could be restored by

  1. A.decreasing the length of the wire
  2. B.increasing the length of the wire
  3. C.increasing the mass per unit length of the wire
  4. D.changing the temperature of the water
Show the answer and explanation

Answer: A (decreasing the length of the wire)

Explanation

In water the load feels an upthrust, so the tension and the frequency fall. Since f = (1/2L)√(T/m), making L smaller raises the frequency back to its original value.