A tuning fork of frequency `340 Hz` is excited and held above a cylindrical tube of lengtyh `120 cm`. It is slowly filled with water. The minimum height of water column required for resonance to be first heart( Velocity of sound `=340 ms^-1`) is.

Options

A. 25 cm
B. 75 cm
C. 45 cm
D. 105 cm

Answer

C

Explanation

`lamda = v/f = (340)/(340)=1 m =100 cm`
Length of air columns may be,
`lambda/4, (3 lambda)/4,(5 lambda)/4 or 25 cm, 75 cm 125cm....`
Minimum height of water column
= `120 -` maximum height of air water column
=` 120 - 75- =45 cm`.