The closed and open organ pipes have same length. When they are vibrating simultaneously in first overtone, they produce four beats. The length of open pipe is made half and that of the closed pipe is made two times the original. Now the number of beats produced if the two pipes are vibrating in their fundamental modes simultaneously is

Fundamental frequency of sonometer wire is ' $n$ '. If the tension and length are increased 3 times and diameter is increased twice, the new frequency will be

A source of sound emits sound wave of frequency ' f ' and moves towards an observer with a velocity $\frac{\mathrm{V}}{3}$ where V is the velocity of sound. If the observer moves away from the source with a velocity $\frac{\mathrm{V}}{5}$ the apparent frequency heard by him will be

An air column is of length 17 cm . The ratio of frequencies of $5^{\text {th }}$ overtone if the air column is closed at one end to that open at both ends is (velocity of sound in air $=340 \mathrm{~ms}^{-1}$ )