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प्रश्न
Answer briefly.
What is Doppler effect?
Explain Doppler Effect.
उत्तर १
The apparent change in the frequency of sound heard by a listener, due to relative motion between the source of sound and the listener is called Doppler effect in sound.
उत्तर २
When the source and the observer are in relative motion with respect to each other and to the medium in which sound propagates, the frequency of the sound wave observed is different from the frequency of the source. This phenomenon is called Doppler Effect.
संबंधित प्रश्न
In discussing Doppler effect, we use the word "apparent frequency". Does it mean that the frequency of the sound is still that of the source and it is some physiological phenomenon in the listener's ear that gives rise to Doppler effect? Think for the observer approaching the source and for the source approaching the observer.
The engine of a train sounds a whistle at frequency v. The frequency heard by a passenger is
Answer briefly.
State the expression for apparent frequency when the source is stationary and the listener is
- moving towards the source
- moving away from the source
Solve the following problem.
A police car travels towards a stationary observer at a speed of 15 m/s. The siren on the car emits a sound of frequency 250 Hz. Calculate the recorded frequency. The speed of sound is 340 m/s.
The sound emitted from the siren of an ambulance has a frequency of 1500 Hz. The speed of sound is 340 m/s. Calculate the difference in frequencies heard by a stationary observer if the ambulance initially travels towards and then away from the observer at a speed of 30 m/s.
Explain red shift and blue shift in Doppler Effect.
Discuss the following case:
Source in motion and Observer at rest
- Source moves towards observer
- Source moves away from the observer
Discuss the following case-
Both are in motion
- Source and Observer approach each other
- Source and Observer resides from each other
- Source chases Observer
- Observer chases Source
The speed of a wave in a certain medium is 900 m/s. If 3000 waves passes over a certain point of the medium in 2 minutes, then compute its wavelength?
Consider a mixture of 2 mol of helium and 4 mol of oxygen. Compute the speed of sound in this gas mixture at 300 K.
A ship in a sea sends SONAR waves straight down into the seawater from the bottom of the ship. The signal reflects from the deep bottom bedrock and returns to the ship after 3.5 s. After the ship moves to 100 km it sends another signal which returns back after 2 s. Calculate the depth of the sea in each case and also compute the difference in height between two cases.
N tuning forks are arranged in order of increasing frequency and any two successive tuning forks give n beats per second when sounded together. If the last fork gives double the frequency of the first (called as octave), Show that the frequency of the first tuning fork is f = (N – 1)n.
A sound source and listener are both stationary and a strong wind is blowing. Is there a Doppler effect?
The difference between the apparent frequency of a source of sound as perceived by the observer during its approach and recession is 2% of the frequency of the source. If the speed of sound in air is 300 ms-1, then the velocity of the source is ______.
Two cars moving in opposite directions approach each other with speed of 22 m/s and 16.5 m/s respectively. The driver of the first car blows a horn having a frequency 400 Hz. The frequency heard by the driver of the second car is [velocity of sound 340 m/s]: ____________.
A railway engine whistling at a constant frequency moves with a constant speed aixi it goes past a stationary observer standing beside the railway track. Then the frequency of (n') of the sound heard by the observer with respect to time (t) can be best represented by which of the following curve?
A source of sound is moving with constant velocity of 30 mis emitting a note of frequency 256 Hz. The ratio of frequencies observed by a stationary observer while the source is approaching him and after it crosses him is ______. (speed of sound in air = 330 m/s)
The pitch of the whistle of an engine appears to drop to`(5/6)^"th"` of original value when it passes a stationary observer. If the speed of sound in air is 350 m/s then the speed of engine is ____________.
If a star appearing yellow starts accelerating towards the earth, its colour appears to be turned ______.
A car sounding a horn of frequency 1000 Hz passes au observer. The ratio of frequencies of the horn noted by the observer before and after passing of the car is 11 : 9. If the speed of sound is 'V', the speed of the car is ______.
A train whistling at constant frequency is moving towards a station at a constant speed V. The train goes past a stationary observer on the station. The frequency n ′ of the sound as heard by the observer is plotted as a function of time t (figure). Identify the expected curve.
The frequency of a car horn encountered a change from 400 Hz to 500 Hz, when the car approaches a vertical wall. If the speed of sound is 330 m/s. Then the speed of car is ______ km/h.
When a sound source of frequency n is approaching a stationary observer with velocity u than the apparent change in frequency is Δn1 and when the same source is receding with velocity u from the stationary observer than the apparent change in frequency is Δn2. Then ______.
When an engine passes near to a stationary observer then its apparent frequencies occurs in the ratio 5/3. If the velocity of engine is ______.
A racing car moving towards a cliff sounds its horn. The sound reflected from the cliff has a pitch one octave higher than the actual sound of the horn. If V is the velocity of sound, the velocity of the car is ______.
The frequency of echo will be ______ Hz if the train blowing a whistle of frequency 320 Hz is moving with a velocity of 36 km/h towards a hill from which an echo is heard by the train driver. The velocity of sound in air is 330 m/s.
The observer is moving with velocity 'v0' towards the stationary source of sound and then after crossing moves away from the source with velocity 'v0'. Assume that the medium through which the sound waves travel is at rest. If v is the velocity of sound and n is the frequency emitted by the source, then the difference between apparent frequencies heard by the observer is ______.
The pitch of the whistle of an engine appears to drop by 20% of its original value when it passes a stationary observer. If the speed of sound in the air is 350 m/s, then the speed of the engine (in m/s) is ______.
