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MCQ practice · SSC Physics Board questions · Chapter 7: Waves and Sound

Chattogram Board 2022

A sound of frequency 2 kHz travels through an iron pipe at a speed of 5130 ms⁻¹. What is the wavelength of that sound?

Think it through first, then pick an option.

  1. a 0.38 m
  2. b 1.28 m
  3. c 2.57 m
  4. d 5.13 m
Answer and explanation

Correct answer: c 2.57 m

λ = v/f = 5130/2000 = 2.565, about 2.57 m.

Why the other options are wrong

  • a 0.38 m: 0.38 is about 2000/5130; the frequency was divided by the speed. λ = v/f.
  • b 1.28 m: 1.28 m = 5130/4000, which assumes 4 kHz. Here it is 2 kHz.
  • d 5.13 m: 5.13 m is for 1 kHz (the book's example). Here it is 2 kHz, so half of that.