Two identical straight wires are stretched so as to produce 6 beats per second when vibrating simultaneously with tensions ' $\mathrm{T}_1$ ' and ' $\mathrm{T}_2$ ' respectively. On changing the tension slightly in one of them, the beat frequency remains unchanged. This will happen when (Given $\rightarrow \mathrm{T}_1>\mathrm{T}_2$ )

An observer moves towards a stationary source of sound with a velocity of one fifth of the velocity of sound. The percentage increase in the apparent frequency is

Two tuning forks when sounded together produce 4 beats per second. One of the forks is in unison with 23 cm length of sonometer wire and other with 24 cm length of the same wire. The frequencies of the two tuning forks are

A pipe open at both ends produces a fundamental frequency $n_1$. When the pipe is kept with $\frac{3^{\text {th }}}{4}$ of its length in water, it produces a note of fundamental frequency $\mathrm{n}_2$. The ratio of $\frac{\mathrm{n}_1}{\mathrm{n}_2}$ is