An open organ pipe of length $L$ vibrates in its fundamental mode. The pressure variation is maximum

A tube of diameter $d$ and of length $l$ unit is open at both ends. Its fundamental frequency of resonance is found to be ${\nu }_1$. The velocity of sound in air is $330 \mathrm{m} {\sec }^{-1}$. One end of the tube is now closed. The lowest frequency of resonance of tube is ${\nu }_2$. Taking into consideration the end correction $\frac{{\nu }_2}{{\nu }_1}$ is

The lengths of two closed organ pipes are $0.750 \mathrm{m}$ and $0.770 \mathrm{m}$. If they are sounded together, $3$ beats