When both source and listener are approaching each other the observed frequency of sound is given by…

When both source and listener are approaching each other the observed frequency of sound is given by $\left(V_L\right.$ and $V_S$ is the velocity of listener and source respectively, $\mathrm{n}_0=$ radiated frequency)
  1. $\mathrm{n}=\mathrm{n}_0\left[\frac{\mathrm{V}+\mathrm{V}_{\mathrm{L}}}{\mathrm{V}-\mathrm{V}_{\mathrm{s}}}\right]$
  2. $\mathrm{n}=\mathrm{n}_0\left[\frac{\mathrm{V}-\mathrm{V}_{\mathrm{L}}}{\mathrm{V}+\mathrm{V}_{\mathrm{s}}}\right]$
  3. $\mathrm{n}=\mathrm{n}_0\left[\frac{\mathrm{V}-\mathrm{V}_{\mathrm{L}}}{\mathrm{V}-\mathrm{V}_{\mathrm{s}}}\right]$
  4. $\mathrm{n}=\mathrm{n}_0\left[\frac{\mathrm{V}+\mathrm{V}_{\mathrm{L}}}{\mathrm{V}+\mathrm{V}_{\mathrm{s}}}\right]$

Solution

Using Dopper's effect formula for approaching frequency when both source and listener are approaching each other, the observed frequency of sound is given by, $\mathrm{n}=\mathrm{n}_0\left[\frac{\mathrm{V}+\mathrm{V}_{\mathrm{L}}}{\mathrm{V}-\mathrm{V}_{\mathrm{s}}}\right]$ ~

Asked in: MHT CET 2023 (09 May Shift 1)

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