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Question
Sound waves of wavelength λ travelling in a medium with a speed of v m/s enter into another medium where its speed is 2v m/s. Wavelength of sound waves in the second medium is ______.
Options
λ
`λ/2`
2λ
4λ
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Solution
Sound waves of wavelength λ travelling in a medium with a speed of v m/s enter into another medium where its speed is 2v m/s. Wavelength of sound waves in the second medium is 2λ.
Explanation:
We know that when a wave passes from one medium to another, its velocity and wavelength change but its frequency remains the same.
We know that `v = fλ`
Therefore, we have
⇒ `f = v/λ` ......(i)
When a sound wave enters another medium, we get
And, ⇒ `f = (2v)/λ^'` ......(ii)
From (i) and (ii), we get
⇒ `v/λ = (2v)/λ^'`
⇒ `1/λ = 2/λ^'`
⇒ `λ^' = 2λ`
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