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

Sylhet Board 2024

For the wave produced:

  1. i. a mechanical wave
  2. ii. wavelength 0.17 m
  3. iii. crests and troughs form

Think it through first, then pick an option.

  1. a i and ii
  2. b i and iii
  3. c ii and iii
  4. d i, ii and iii
Answer and explanation

Correct answer: d i, ii and iii

The board answer. i: sound is a mechanical wave. ii: λ = v/f = 340/2000 = 0.17 m. iii: in exams a compression is taken as the crest and a rarefaction as the trough. The book does not use these names, so this is a beyond-the-book fact.

Why the other options are wrong

  • a i and ii: i and ii are true, but the board counts iii as true too: in exams a compression is called a crest and a rarefaction a trough. So i and ii alone fall short.
  • b i and iii: ii cannot be left out: λ = v/f = 340/2000 = 0.17 m, so ii is true.
  • c ii and iii: i cannot be left out: sound is a mechanical wave and needs a medium.

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