$A$ photon of energy $8\, eV$ is incident on a metal surface of threshold frequency $1.6 \times 10^{15}\, Hz$. The maximum kinetic energy of the emitted photoelectrons is ............. $eV$ $(h = 6.6 \times 10^{-34}\, Js)$.

The ratio of the speed of the electrons in the ground state of hydrogen to the speed of light in vacuum is

The amplitude of vibration of a particle is given by $a_m = a_0 / (a\omega^2 - b\omega + c)$,where $a_0$,$a$,$b$,and $c$ are positive constants. The condition for a single resonant frequency is:

The suspension of slaked lime in water is known as

If $z_1, z_2$ are two complex numbers satisfying $\left|\frac{z_1-3 z_2}{3-z_1 \bar{z}_2}\right|=1$ and $\left|z_1\right| \neq 3$,then $\left|z_2\right|$ is equal to

When an air bubble of radius $r$ rises from the bottom to the surface of a lake, its radius becomes $\frac{5r}{4}$. If the atmospheric pressure is equal to the pressure exerted by a $10 \ m$ height of water column, and the temperature remains constant while surface tension is neglected, what is the depth of the lake (in $m$)?