The equation of a transverse wave propagating on a stretched string is given by $y=3 \sin (4 x+200 t)$, where $x$ and $y$ are in metre and the time ' $t$ ' is in second. If the tension applied to the string is 500 N , the linear density of the string is

The fundamental frequency of transverse wave of a stretched string subjected to a tension $T_1$ is 300 Hz . If the length of the string is doubled and subjected to a tension of $T_2$, the fundamental frequency of the transverse wave in the string becomes 100 Hz , then $T_2: T_1=$

(Linear density of the string is constant)

Two sound waves each of intensity $I$ are superimposed. If the phase difference between the waves is $\frac{\pi}{2}$, then the intensity of the resultant wave is