Question

A pipe open at both ends has a fundamental frequency of 2Hz. If the pipe is closed at one end and half filled with water, what will be the fundamental frequency?

(a) 0.5Hz

(b) 2Hz

(c) 4Hz

(d) 1Hz

I have been asked this question in class test.

Question is from Reflection of Waves topic in chapter Waves of Physics – Class 11

Answer 1

Right option is (b) 2Hz

The best explanation: The fundamental frequency in the first case is given by: f1 = v/2L.

In the second case length becomes half & one end is closed,   

so fundamental frequency f2 = v/(4L/2)

= v/2L = f1.

So the value of f2 = 2Hz.