When both source of sound and observer approach each other with a speed equal to $10 \%$ of the speed of sound, then the percentage change in frequency heard by the observer is nearly

A sound wave of frequency 500 Hz travels between two points $X$ and $Y$ separated by a distance of 600 m in a time of 2 s . The number of waves between the points $X$ and $Y$ are

The equation of a transverse wave propagating along a stretched string of length 80 cm is $y=1.5 \sin \left\{\left(5 \times 10^{-3} x\right)+20 t\right\}$, here ' $x$ ' and ' $y$ ' are in cm and the time ' $t$ ' is in second. If the mass of the string is 3 g , then the tension in the string is 80 cm

If a travelling wave is given by $y(x, t)=0.5 \sin (70.1 x-10 \pi t)$, where $x$ and $y$ are in metre the time $t$ is in second, then the frequency of the wave is