There is a long linear source of sound whose power is $P$ and length is $L$. At point $A$,the sound level is $80 \ dB$. Then at point $B$,the sound level will be .... $dB$.

The clocktower ("ghantaghar") of Dehradun is famous for the sound of its bell, which can be heard, albeit faintly, up to the outskirts of the city $8 \,km$ away. Let the intensity of this faint sound be $30 \,dB$. The clock is situated $80 \,m$ high. The intensity at the base of the tower is ............. $\,dB$.

$A$ stone is dropped in still water,creating a circular wave pattern that spreads outward. If $r$ is the distance from the center of this circular pattern,the amplitude of the wave is proportional to ........

$A$ wave can transmit ...... from one place to another.

$A$ transverse wave is passing through a stretched string with a speed of $20 \ m/s$. The tension in the string is $20 \ N$. At a certain point $P$ on the string,it is observed that energy is being transferred at a rate of $40 \ mW$ at a given instant. Find the speed of point $P$.

$A$ surface of area $S$ is placed perpendicular to the direction of travel of a plane wave. The energy per unit time intercepted by the surface is $E$ when the amplitude of the wave is $A$. The area of the surface is reduced to $\frac{1}{2} S$ and the amplitude of the wave is increased to $2A$. What is the energy per unit time intercepted by this smaller surface?