A train standing at the outer singal of a railway station blows a whistle of frequency 400 Hz in still air. (i) What is frequency of the whistle for a platform observer when the train (a) approaches the platform with a speed of 10 m/s, (b) recedes from the platform with a speed of 10 m/s. (ii) What is the speed of sound in each case if the speed of sound in still air is 340 m/s.
Text Solution
Verified by Experts
(i) Here, n= 400 Hz, `v = 340 m//s` (a) When train approaches the platform, `v_(s) = 10 m//s` So, required frequency `=v/(v-v_(s))xxn=(340xx400)/(340-10)=412.12" Hz"` (b) When train recedes from the platfrom. `v_(s) = 10 m//s` Hence, required frequency `=v/(v-v_(s))xxn=(340xx400)/(340+10)= 388.6" Hz"` (ii) The speed of sound in both the cases is same.
Topper's Solved these Questions
DOPPLER EFFECT IN SOUND
CHHAYA PUBLICATION|Exercise EXAMINATION ARCHIVE WITH SOLUTIONS (NEET)|2 Videos
To hear the echo of a sound, the minimum distance between, listener and the reflector should be speed of sound in air =340 m/s)
A train moving with a velocity v is passing a station. A passenger standing on the station notices that the whistle emitted by the train changes its frequency by 50 Hz when it passes him. Given that the frequency of the whistle when the train is at rest with respect to the passenger is 500 Hz and the velocity of sound in air is 330 m/sec, the velocity of the train is
A passenger in a train with speed 72 km/h observed another train coming from the opposite direction with speed 32.4 km/ h . What is the length of the second train if it crosses the passenger in 10s ?
CHHAYA PUBLICATION-DOPPLER EFFECT IN SOUND -CBSE SCANNER
