For sound waves, if the number of nodes for the $5^{\text {th }}$ harmonic of an open-ended pipe is $n$ and that for the $9^{\text {th }}$ harmonic of the same pipe with one of its ends closed is $m$, the ratio $\frac{n}{m}$ is

For a travelling harmonic wave

$y(x, t)=2.0 \cos 2 \pi(10 t-0.0080 x+0.35)$, where $x$ and $y$ are in cm and $t$ in $s$. The phase difference between oscillatory motion of two points separated by a distance of 0.5 m is:

A pipe open at both ends has a fundamental frequency $f$ in air. The pipe is now dipped vertically in a water drum to half of its length. The fundamental frequency of the air column is now equal to:

The displacement of a travelling wave $$y=C \sin \frac{2 \pi}{\lambda}$$ (at $$-x$$) where $$t$$ is time, $$x$$ is distance and $$\lambda$$ is the wavelength, all in S.I. units. Then the frequency of the wave is