Q. A pipe closed at one end and open at the other end, resonate with sound waves of frequency 135 Hz and also 165 Hz, But not with any wave of frequency intermediate between these two. Then the frequency of the fundamental note is

A) 30 Hz
B) 15 Hz
C) 60 Hz
D) 7.5 Hz
Explanation

(b) In a closed pipe, resonance frequency $n = (2\ r - 1)v = 4l = 135\ and\ 165$.
The lowest frequency must be highest common factor of $135\ and\ 165$, which is $15\ Hz$.

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.

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