# An open-ended tube is 7.8 m long. What is the wavelength of a third harmonic standing wave?

Mar 16, 2018

$5.2 m$

#### Explanation:

For an open ended tube,at both the ends antinodes are present,so for $1$st harmonic it's length $l$ is equals to distance between two antinodes i.e $\frac{\lambda}{2}$ where, $\lambda$ is the wavelength.

So,for $3$ rd harmonic $l = \frac{3 \lambda}{2}$

Or, $\lambda = \frac{2 l}{3}$

Given, $l = 7.8 m$

So,lambda =(2×7.8)/3=5.2m