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प्रश्न
Explain why, the flash of lightning reaches us first and the sound of thunder is heard a little later.
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उत्तर
Since light travels faster than sound, the flash of lightning is seen first and the sound of thunder is heard thereafter.
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संबंधित प्रश्न
Name the device which is used to address a small gathering of people.
On which day, a hot day or a cold day, an echo is heard sooner ? Give reason for your answer.
An echo-sounder in a trawler (fishing boat) receives an echo from a shoal of fish 0.4 s after it was sent. If the speed of sound in water is 1500 m/s, how deep is the shoal ?
Which of the following device does not work on the multiple reflections of sound waves ?
Explain by giving a scientific reason.
We cannot hear the echo produced in a classroom.
Answer the following question in your own words.
What should be the dimensions and the shape of classrooms so that no echo can be produced there?
Assertion: The sound which we hear again is called Echo.
Reason: The sensation of sound (Echo) persists in our brain for about 1 s.
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?
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
