The fundamental frequency of a closed pipe is 400 Hz . If $\left(\frac{1}{3}\right)^{\text {rd }}$ length of the pipe is filled with water, the frequency of the $2^{\text {nd }}$ harmonic of the pipe will be (Neglect end correction)

At poles, a stretched wire of a given length vibrates in unison with a tuning fork. At the equator, for same setting, to produce resonance with same fork, the vibrating length of wire

Two tuning forks of frequencies 256 Hz and 258 Hz are sounded together. The time interval between two consecutive maxima is

If a source emitting waves of frequency ' $F$ ' moves towards an observer with a velocity $\frac{\mathrm{V}}{3}$ and the observer moves away from the source with a velocity $\frac{\mathrm{V}}{4}$, the apparent frequency as heard by the observer will be ( $\mathrm{V}=$ velocity of sound)