In an orchestra,the musical sounds of different instruments are distinguished from one another by the characteristic of

What is a crest?

$(i)$ What causes the reverberation of thunder sound?
$(ii)$ $A$ $SONAR$ device on a submarine sends a signal and receives an echo $5 \, s$ later. Calculate the speed of sound in water if the distance of the object from the submarine is $3625 \, m$.

What is a transverse wave?

$(a)$ Which of the following frequencies are audible to human ears: $2 \, Hz$,$5 \, Hz$,$20 \, Hz$,$200 \, Hz$,$2000 \, Hz$?
$(b)$ How are moths of certain families able to escape capture?

$A$ source is producing $1500$ sound waves in $3$ seconds. If the distance covered by a compression and an adjacent rarefaction is $68 \, cm$,find $(a)$ frequency,$(b)$ wavelength,and $(c)$ velocity of the sound wave.