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The two nearest harmonics of a tube closed at one end and open at other end are 220 Hz and 260 Hz. What is the fundamental frequency of the system?

Asked in NEET 2017 · Closed and open pipes

• (1) 20 Hz
• (2) 30 Hz
• (3) 40 Hz
• (4) 10 Hz

Step-by-step solution

Why the other options are wrong

• (2) A fundamental of 30 Hz would give the odd harmonics 30, 90, 150, 210, 270 Hz — and neither 220 nor 260 is among them.
• (3) Is the gap itself. A closed pipe sounds only odd harmonics, so successive ones differ by 2f₀, not f₀.
• (4) A fundamental of 10 Hz would give 10, 30, 50, ... 210, 230, 250 Hz, a gap of 20 Hz, and again 220 and 260 never appear.

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