$A$ pipe closed at one end has a length of $0.8 \,m$. At its open end, a $0.5 \,m$ long uniform string is vibrating in its $2^{nd}$ harmonic and it resonates with the fundamental frequency of the pipe. If the tension in the wire is $50 \,N$ and the speed of sound is $320 \,m/s$, what is the mass of the string (in $\,g$)?

Match Column-$1$ with Column-$2$.

Column-$1$	Column-$2$
$(a)$ Light waves	$(i)$ Mechanical and transverse.
$(b)$ Sound waves	$(ii)$ Mechanical and longitudinal.
$(c)$ Earthquake waves	$(iii)$ Non-mechanical and transverse.
$(d)$ Waves on a tense string	$(iv)$ Mechanical,transverse and longitudinal.

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 $A$?

$Assertion :$ Transverse waves are produced in a very long string fixed at one end. Only a progressive wave is observed near the free end.
$Reason :$ Energy of the reflected wave does not reach the free end.

Two tuning forks $A$ and $B$ give $5$ beats per second. Fork $A$ resonates with a closed air column $20 \ cm$ long and fork $B$ with an open air column $40.5 \ cm$ long. Neglecting end correction,the frequencies of tuning forks $A$ and $B$ are respectively.

$A$ pipe open at one end has a length of $0.8 \text{ m}$. At the open end of the tube, a string $0.5 \text{ m}$ long is vibrating in its first overtone and resonates with the fundamental frequency of the pipe. If the tension in the string is $50 \text{ N}$, what is the mass of the string (in $\text{ g}$)? (Neglect end correction, Speed of sound = $320 \text{ m/s}$)