A pipe 20 cm long is closed at one end. Which harmonic mode of the pipe is resonantly excited by a source of 1237.5 Hz ? (sound velocity in air `=330ms^(-1))`

Options

A. Second harmonic
B. Third harmonic
C. Fourth harmonic
D. Fifth harmonic

Answer

B

Explanation

For a closed pipe ,
`n = V/(4L) = (330)/(4 xx 20 xx 10^(-2)) `
` = (330 xx 100)/30 = 412.5 ` Hz
This is the fundamental frequency .
`:. (n_("given"))/(n_("fundamental")) = (1237.5)/(412.5) = 3`
` :. ` Third harmonic is resonantly excited by the source.