If a microwave and an ultrasonic sound wave have the same wavelength, the ratio of their frequencies is approximately:

The ratio of intensities between two coherent sound sources is $4:1$. The difference of loudness in $dB$ between maximum and minimum intensities when they interfere in the space is ..........

The time of reverberation of a room $A$ is $1 \; s$. What will be the time (in seconds) of reverberation of a room,having all the dimensions double of those of room $A$?

$A$ wire of linear mass density $\mu = 9.8 \times 10^{-3} \, kg \, m^{-1}$ passes over a frictionless light pulley fixed on the top of a frictionless inclined plane which makes an angle of $30^{\circ}$ with the horizontal. Masses $m$ and $M$ are tied at the two ends of the wire such that $m$ rests on the plane and $M$ hangs freely vertically downwards. The entire system is in equilibrium and a transverse wave propagates along the wire with a velocity of $100 \, m \, s^{-1}$. Choose the correct option for $m$ in $kg$.

Following are expressions for four plane simple harmonic waves:
$(i) \, y_1 = A \cos 2\pi \left( n_1 t + \frac{x}{\lambda_1} \right)$
$(ii) \, y_2 = A \cos 2\pi \left( n_1 t + \frac{x}{\lambda_1} + \frac{1}{2} \right)$
$(iii) \, y_3 = A \cos 2\pi \left( n_2 t + \frac{x}{\lambda_2} \right)$
$(iv) \, y_4 = A \cos 2\pi \left( n_2 t - \frac{x}{\lambda_2} \right)$
The pairs of waves which will produce destructive interference and stationary waves respectively in a medium are:

Fill in the blanks:
$(i)$ If the fundamental frequency of a given closed pipe is $50 \ Hz$,then the frequency for the second overtone is ...... .
$(ii)$ The speed of sound in air at $STP$ is ...... .
$(iii)$ In the case of sound waves,in order to experience beats quite clearly,the value of the beat frequency $|f_1 - f_2|$ should not be greater than ...... .