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Which observation best supports the idea that sound is a mechanical wave? (i) Sound shows reflection (ii) Sound needs a medium to propagate (iii) Sound has frequency (iv) Sound carries energy
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Answer: (ii)
- (ii) correct — needing a medium is the defining feature of a mechanical wave.
- Reflection, frequency and carrying energy are true of sound but are shared by many waves, so they do not specifically prove it is mechanical.
Option
Verdict & why
(i)
Sound shows reflection
Wrong
— light also reflects, and light is
not
a mechanical wave.
(ii)
Sound needs a medium to propagate
Correct
— needing a material medium is the
defining
test of a mechanical wave.
(iii)
Sound has frequency
Wrong
— every wave, mechanical or not, has a frequency.
(iv)
Sound carries energy
Wrong
— all waves carry energy, including light.
