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

In a pipe closed at one end, air column is vibrating in its second overtone. The column has

The fundamental frequency of a sonometer wire is 50 Hz for some length and tension. If the length is increased by $25 \%$ by keeping tension same then frequency change of second harmonic is

When source of sound and observer both are moving towards each other, the observer will hear