A person observes two moving trains. First reaching the station and another leaves the station with equal speed of 30 m/s. If both trains emit sounds of frequency 300 Hz, difference of frequencies heard by the person will be (speed of sound in air 330 m/s) (a) 80 Hz (b) 75 Hz (c) 55 Hz (d) 45 Hz

Answer: (c). Approaching train: f₁ = 300 × (330)/(300) = 330 Hz. Receding train: f₂ = 300 × (330)/(360) = 275 Hz. Difference = 55 Hz. So the answer is (c) 55 Hz.

A person observes two moving trains. First reaching the station and… | MHT CET 2025 (5 May, Shift 2)

Q13MHT CET 2025 · 5 MAY · SHIFT 2Easy

Doppler Effect

A person observes two moving trains. First reaching the station and another leaves the station with equal speed of $30\text{ m/s}$ . If both trains emit sounds of frequency 300 Hz, difference of frequencies heard by the person will be (speed of sound in air $330\text{ m/s}$ )

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Answer: (c)

Approaching train: $f_1 = 300 \times \frac{330}{300} = 330$ Hz.
Receding train: $f_2 = 300 \times \frac{330}{360} = 275$ Hz.
Difference $= 55$ Hz. So the answer is (c) 55 Hz.

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Doppler Effect question from MHT CET 2025 (5 May, Shift 2)

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