Advertisements
Advertisements
Question
A radio signal, sent towards the surface of the moon, is received in 2.5 seconds. If the speed of the radio waves is 3 × 108 ms−1, find the distance of the moon from the earth.
Advertisements
Solution
Let ‘d’ be the required distance. The radio waves then travel a total distance 2d (to and from the moon) in 2.5 seconds.
Hence,
`(2"d")/2.5` = Speed = 3 × 108
d = `3xx10^8xx2.5/2` metre
= 3.75 × 108 metre.
RELATED QUESTIONS
Define frequency term in relation to a wave.
A wave passes from one medium to another medium. Mention one property of the wave out of speed, frequency or wavelength which does not change.
State the use of echo by a bat, dolphin and fisherman.
Name the waves which are used in sonar to find the depth of a sea. Give one reason for their use.
Write the approximate value of the speed of sound in air.
What are fishing boats?
(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?
Explain why, the ceilings of concert halls are curved.
