The wavelengths of two notes in air are $\frac{36}{195} ~m$ and $\frac{36}{193} ~m$. Each note produces $10$ beats per second separately with a third note of fixed frequency. The velocity of sound in air in $m/s$ is

If $f: R \rightarrow R$ is defined by $f(x) = x - [x]$,where $[x]$ is the greatest integer not exceeding $x$,then the set of points of discontinuity of $f$ is

Two capillary tubes of same diameter are put vertically one each in two liquids whose relative densities are $0.8$ and $0.6$ and surface tensions are $60$ and $50 \, dyne/cm$ respectively. The ratio of the heights of the liquids in the two tubes $\frac{h_1}{h_2}$ is:

$A$ rifle of $20 ~kg$ mass can fire $4$ bullets per second. The mass of each bullet is $35 \times 10^{-3} ~kg$ and its final velocity is $400 ~ms^{-1}$. What force must be applied on the rifle so that it does not move backwards while firing the bullets (in $~N$)?

In $P-N$ junction,the barrier potential offers resistance to

In which group of organisms do the cell walls form two thin overlapping shells that fit together?