Two pulses travel in mutually opposite directions in a string with a speed of $2.5 \ cm/s$ as shown in the figure. Initially,the pulses are $10 \ cm$ apart. What will be the state of the string after two seconds?

The amplitude and phase of a wave that is formed by the superposition of two harmonic travelling waves,$y_1(x, t) = 4 \sin(kx - \omega t)$ and $y_2(x, t) = 2 \sin(kx - \omega t + \frac{2\pi}{3})$,are (Take the angular frequency of initial waves same as $\omega$):

$A$ sound wave of wavelength $32 \ cm$ enters the tube at $S$ as shown in the figure. Then the smallest radius $r$ so that a minimum of sound is heard at detector $D$ is ... $cm$.

What is interference? Define its types.

The sources of sound $A$ and $B$ produce a wave of $350 Hz$ in the same phase. $A$ particle $P$ is vibrating under the influence of these two waves. If the amplitudes at $P$ produced by the two waves are $0.3 mm$ and $0.4 mm$,the resultant amplitude of the point $P$ will be,when $AP-BP=25 cm$ and the velocity of sound is $350 m s^{-1}$. (in $mm$)

Two waves of equal amplitude and frequency interfere with each other. The ratio of intensity when the two waves arrive in phase to that when they arrive $90^{\circ}$ out of phase is: