⚛️ Physics · Waves · NEET & JEE

Two open pipes of length L₁ and L₂ (L₁ < L₂) are sounded together. Beats per second = 5. If fundamental freq of shorter is 100 Hz, L₂/L₁ equals:

Answer: 19/20.

A 0.95
B 20/21
C 19/20
D 21/20

Correct answer: C. 19/20

Explanation: f₁=100, f₂=f₁-5=95. f₂/f₁=95/100=19/20. Since f=v/(2L), L proportional to 1/f. L₂/L₁=f₁/f₂=100/95=20/19. So L₁/L₂=19/20.

A standing wave forms from two identical waves travelling in opposite directions and interfering; nodes (always zero displacement) and antinodes (maximum displacement) stay fixed in place, unlike a travelling wave where the whole pattern moves.

Concept context

Wave types, superposition, standing waves, Doppler effect, and sound intensity.

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Two open pipes of length L1 and L2 (L1 < L2) are sounded together. Beats per second = 5. If fundamental freq of shorter is 100 Hz, L2/L1 equals:

Concept context

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Two open pipes of length L₁ and L₂ (L₁ < L₂) are sounded together. Beats per second = 5. If fundamental freq of shorter is 100 Hz, L₂/L₁ equals: