Sound waves travel at $350 \mathrm{~m} / \mathrm{s}$ through a warm air and at $3500 \mathrm{~m} /…

Sound waves travel at $350 \mathrm{~m} / \mathrm{s}$ through a warm air and at $3500 \mathrm{~m} / \mathrm{s}$ through brass. The wavelength of a $700 \mathrm{~Hz}$ acoustic wave as it enters brass from warm air
  1. increases by a factor 20
  2. increases by a factor 10
  3. decreases by a factor 20
  4. decreases by a factor 10

Solution

Velocity of sound $y=n \lambda$ $\begin{aligned} & \frac{y_1}{y_2}=\frac{n_1 \lambda_1}{n_2 \lambda_2} \quad \text { (but } n_1=n_2 \text { ) } \\ & \lambda_2=\lambda_1 \frac{y_2}{y_1}=\lambda_1 \times 10 \\ & \lambda_2=10 \lambda_1 \end{aligned}$ *

Asked in: NEET 2011 (Screening)

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