The second overtone of an open pipe $A$ and a closed pipe $B$ have the same frequencies. The ratio of the fundamental frequency of $A$ to the fundamental frequency of $B$ is

An engine driver moving towards a wall with a velocity of $50 \mathrm{m} {\mathrm{s}}^{–1}$ emits a note of frequency $1.2 \mathrm{kHz}$. The frequency of note after reflection from the wall as heard by the engine driver when the speed of sound in air is $350 \mathrm{m} {\mathrm{s}}^{–1}$ is

An observer moves on a circle as shown in the figure and a small sound source is at $S$. Let at ${\upsilon }_1$, ${\upsilon }_2$, ${\upsilon }_3$ be the frequencies heard when the observer is at $A$, $B$, and $C$, respectively.