A progressive wave of frequency 400 Hz is travelling with a velocity $336 \mathrm{~m} / \mathrm{s}$. How far apart are the two points which are $60^{\circ}$ out of phase?

The end correction of resonance tube is 1 cm. If the shortest length resonating with a tuning fork is 15 cm , the next resonating length will be

If ' $l$ ' is the length of pipe, ' $r$ ' is the internal radius of the pipe and ' $v$ ' is the velocity of sound in air then fundamental frequency of open pipe is

A violin emits sound waves of frequency ' $n_1$ ' under tension T. When tension is increased by $44 \%$, keeping the length and mass per unit length constant, frequency of sound waves becomes ' $\mathrm{n}_2$ '. The ratio of frequency ' $\mathrm{n}_2$ ' to frequency ' $n_1$ ' is