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प्रश्न
State two conditions necessary for hearing an echo.
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उत्तर
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The persistence of hearing for human ears is 0.1 second. This means that we can hear two sound waves clearly if the time interval between the two sounds is at least 0.1 s. Thus, the minimum time gap between the original sound and an echo must be 0.1 s.
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The above criterion can be satisfied only when the distance between the source of the sound and the reflecting surface would satisfy the following equation:
Velocity = `"Distance travelled by sound"/"Time taken"`
V = `(2"d")/"t"`
d = `("vt")/2`
Since, t = 0.1 second, then d= `("v"xx0.1)/2` = `"v"/20`
संबंधित प्रश्न
Does sound follow the same laws of reflection as light does? Explain.
When a sound is reflected from a distant object, an echo is produced. Let the distance between the reflecting surface and the source of sound production remains the same. Do you hear echo sound on a hotter day?
What is meant by an echo?
Which property of sound leads of the formation of echoes ?
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Echoes are caused by the ...................... of sound.
The speed of sound in water is 1500 metres per second. How far away from an under-sea rock should a deep sea diver be so that he can hear his own echo ?
What is an echo ? How is echo formed ?
Which of the following device does not work on the multiple reflections of sound waves ?
Answer the following question in your own words.
What is an echo?
A man is standing between two vertical walls 680 m apart. He claps his hands and hears two distinct echoes after 0.9 seconds and 1.1 seconds respectively. What is the speed of sound in the air?
What are the medical applications of echo?
When sound is reflected from a distant object, an echo is produced. Let the distance between the reflecting surface and the source of sound remain the same. Do you hear an echo sound on a hotter day? Justify your answer.
______ allows bats to navigate through dark caves and find insects for food.
What is an echo? Write the conditions to hear an echo.
Numerical problems:
An echo returned in 3s. What is the distance of the reflecting surface from the source given that the speed of sound is 330 ms-1?
Answer the following question in your own words.
What factors are important to get a distinct echo?
Rohan conducted experiments on echo in different media. He observed that a minimum distance of 'x' meters is required for the echo to be heard in oxygen and 'y' meters in benzene. Compare 'x' and 'y'. Justify your answer.
Speed of sound in oxygen: 340 ms-1
Speed of sound in benzene: 200 ms-1
