Question:medium
A person observes two moving trains. 'A' reaching the station and 'B' leaving the station with equal speed of 30m/s. If both trains emit sounds with frequency 300 Hz, (speed of sound = 330 m/s) difference of frequencies heard by the person will be
A person observes two moving trains. 'A' reaching the station and 'B' leaving the station with equal speed of 30m/s. If both trains emit sounds with frequency 300 Hz, (speed of sound = 330 m/s) difference of frequencies heard by the person will be
Show Hint
One train approaches and one recedes, so use the Doppler formula for each.
Updated On: Oct 1, 2026
- \(10 \text{Hz}\)
- \(33 \text{Hz}\)
- \(55 \text{Hz}\)
- \(80 \text{Hz}\)
Show Solution
The Correct Option is C
Solution and Explanation
Step 1: Compute ratios
Approaching: $\frac{330}{330-30} = 1.1$ gives $330$ Hz. Receding: $\frac{330}{330+30} = \frac{11}{12}$ gives $275$ Hz.
Step 2: Subtract
$55$ Hz. Option (C).
Final Answer:
55 Hz. \[ \boxed{\text{(C)}\ 55\ \text{Hz}} \]
Approaching: $\frac{330}{330-30} = 1.1$ gives $330$ Hz. Receding: $\frac{330}{330+30} = \frac{11}{12}$ gives $275$ Hz.
Step 2: Subtract
$55$ Hz. Option (C).
Final Answer:
55 Hz. \[ \boxed{\text{(C)}\ 55\ \text{Hz}} \]
Was this answer helpful?
0
Top Questions on doppler effect
- A passenger is sitting in a fast moving train. The engine of the train blows a whistle of frequency N. If the apparent frequency of sound heard by the passengers is \( N' \), then:
- MHT CET - 2025
- Physics
- doppler effect
- A car P travelling at 20 \(ms^{–1}\) sounds its horn at a frequency of 400 Hz. Another car Q is travelling being the first car in the same direction with a velocity 40 \(ms^{–1}\) . The frequency heard by the passenger of the car Q is approximately [Take, velocity of sound = 360 \(ms^{–1}\) ]
- JEE Main - 2023
- Physics
- doppler effect
- A source has wavelength 60 cm when it is stationary. If the speed of sound in air is 320m s⁻¹ and the source moves with speed 20m s⁻¹, the wavelength in the forward direction will be
- BITSAT - 2010
- Physics
- doppler effect
A source of sound S emitting waves of frequency 100Hz and an observer O are located at some distance from each other. The source is moving with a speed of 19.4m s⁻1 at an angle of 60^∘ with the source–observer line as shown in the figure. The observer is at rest. Find the apparent frequency observed by the observer. (Velocity of sound in air =330m s⁻1).
- BITSAT - 2020
- Physics
- doppler effect
- Want to practice more? Try solving extra ecology questions todayView All Questions