Advertisements
Advertisements
प्रश्न
Why is an echo not heard when the distance between the source of sound and reflection body is less than 10 m?
Advertisements
उत्तर
The impression of sound lasts on the eardrum for `1/10` of a second. In `1/10` of a second, the sound travels a distance `332"m"/"s"xx1/10"s"` = 33.2. Thus, the minimum distance between the source of the sound and the reflecting body should be `33.2/2` = 16.6 m.
As the distance 10 m is far less than 16.6 m, therefore the ear cannot make out when the original sound had died and echo has been received. Thus, no echo is heard.
संबंधित प्रश्न
What is the shape of a soundboard kept behind the speaker on the stage of a big hall ?
What is a bulb horn ? Name the principle on which a bulb horn works.
What is a stethoscope ? Name the principle on which a stethoscope works.
What do you mean by reflection of sound? State one condition for the reflection of a sound wave. Name a device in which reflection of sound wave is used.
Mention two properties of a wave, one property which varies and the other which remains constant when the wave passes from one medium to another.
(i) A man stands at a distance of 68 m from a cliff and fires a gun. After what time interval will he hear the echo, if the speed of sound in air is 340 ms−1?
(ii) If the man had been standing at a distance of 12 m from the cliff would he have heard a clear echo?
A sound wavelength of 0.332 m has a time period of 10−3 s. If the time period is decreased to 10−4 s, calculate the wavelength and frequency of the new wave.
A sound wave whose frequency is 5000 Hz travels in air and then hits the water surface. The ratio of its wavelengths in water and air is ______.
What is meant by an echo? Explain.
Match the following:
| 1. | Stethoscope | a. | Repeated reflections |
| 2. | Echogram | b. | Multiple reflections |
| 3. | SONAR | c. | Ultrasonic waves |
| 4. | Reverberation | d. | Speed of underwater objects |
