$A$ stone thrown into still water creates a circular wave pattern moving radially outwards. If $r$ is the distance measured from the centre of the pattern, the amplitude of the wave varies as

$A$ is singing a note and at the same time $B$ is singing a note with exactly one-eighth the frequency of the note of $A$. If the energies of the two sounds are equal,the amplitude of the note of $B$ is:

The relation between time and displacement for two particles is given by
${y_1} = 0.06 \sin 2\pi (1.04t + {\phi _1})$
${y_2} = 0.03 \sin 2\pi (1.04t + {\phi _2})$
The ratio of the intensity of the waves produced by the vibrations of the two particles will be

Do waves carry momentum also along with energy?

$A$ point source is emitting sound waves of intensity $16 \times 10^{-8} \text{ W m}^{-2}$ at a distance of $1 \text{ m}$ from the source. The difference in intensity (magnitude only) at two points located at distances of $2 \text{ m}$ and $4 \text{ m}$ from the source respectively will be . . . . . . $\times 10^{-8} \text{ W m}^{-2}$.

The intensity level at a distance of $200 \ cm$ from a sound source is $80 \ dB$. If there is no loss of acoustic power in the air and the threshold intensity of hearing is $10^{-12} \ W/m^2$,what is the intensity level at a distance of $400 \ cm$ from the source (in $dB$)?