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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.
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उत्तर
The frequency of the sound is still that of the source. However, the frequency of the vibrations received by the observer changes due to relative motion.
If both (the observer and the source) move towards each other, then the frequency of the vibrations received by the observer will be higher compared to the original frequency.
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संबंधित प्रश्न
A narrow sound pulse (for example, a short pip by a whistle) is sent across a medium. (a) Does the pulse have a definite (i) frequency, (ii) wavelength, (iii) speed of propagation? (b) If the pulse rate is 1 after every 20 s, (that is the whistle is blown for a split of second after every 20 s), is the frequency of the note produced by the whistle equal to 1/20 or 0.05 Hz
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.
What is meant by the Doppler effect?
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
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.
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.
How do animals sense impending danger of hurricane?
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 ______.
In a quink tube experiment, a tuning fork of frequency 300 Hz is vibrated at one end. It is observed that intensity decreases from maximum to 50% of its maximum value, as tube is moved by 6.25 cm. Velocity of sound is ______ m/s.
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 ______.
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.
A whistle producing sound waves of frequencies 9500 Hz and above is approaching a stationary person with speed v ms-1. The velocity of sound in air is 300 ms-1. If the person can hear frequencies up to a maximum of 10,000 HZ, the maximum value of v up to which he can hear the whistle is ______.
The pitch of whistle of an engine appears to drop by 30% of the original value when it passes a stationary observer. If speed of sound in air is 350 m/s, then the speed of engine in m/s is ______.
