 # Lakhmir Singh Solutions Class 9 Physics Solutions for Exercise in Chapter 5 - Sound

a) Explain the terms ‘crests’ and ‘trough’ of a wave? What type of waves consists of crests and troughs?

b) The flash of a gun is seen by a man 3 seconds before the sound is heard. Calculate the distance of the gun from the man.

a) The crest is a part of a transverse wave which is the elevation experienced by the wave from the line which is above zero disturbance. The trough is also a part of a transverse wave which is the depression experienced by the wave from the line which is below zero disturbance.

b) Speed of sound = 332 m/s

Time = 3s

Speed = distance/time

Distance = (Speed) (time) = 996 m

Video transcript
"hey guys welcome to lido q a video i am vinit your lido tutor glad to bring you this question on your screen explain the terms crest and trough of a wave what type of wave consists of crests and trough okay so crest and troughs both are parts of transverse wave waves right the crest is the elevation experienced by the wave the crest is the elevation experienced by the wave by the wave from the line which is above zero disturbance from the line above zero disturbance and trough is a part tough is the depression depression experienced by the way from the line which is below zero disturbance so trough is the depression experienced by the wave by the wave from the line below zero disturbance now let us look at part b part b is the flash of a gun is seen by a man in three seconds before the sound is heard calculate the distance of the gun from the man so here the speed of sound in air is so speed we all know is 332 meter per second time is 3 seconds therefore distance is given by speed into time so this is equal to 332 into 3 that is equal to 996 meter if you still have it out please leave a comment below do like the video and subscribe to our channel i'll see you in our next video until then bye guys keep practicing"
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