The frequency of the third harmonic of a closed. . .

Question : The frequency of the third harmonic of a closed organ pipe is equal to which of the overtone

(a) Fourth 

(b) Third

(c) Second 

(d) First

Doubt by Nafisha

Solution : 

We know, in a closed organ pipe the frequency of nth harmonic is given by 

𝜈'=(2n-1)v/4L

For n = 1
𝜈'=v/4L

This frequency is called First Harmonic (Fundamental Frequency)

For n = 2

𝜈'=3v/4L

This is called Third Harmonic or First overtone. 

Clearly, frequency of the third harmonic of a closed organ pipe is equal to First Overtone. Hence, (d) First, would be the correct option.