The velocity of photon is proportional to (where $v$ is frequency)
$\frac{{{\nu ^2}}}{2}$
$\frac{1}{{\sqrt \nu }}$
$\sqrt \nu $
$v$
Both the nucleus and the atom of some element are in their respective first excited states. They get de-excited by emitting photons of wavelengths $\lambda _N,\,\lambda _A$ respectively. The ratio $\frac{{{\lambda _N}}}{{{\lambda _A}}}$ is closest to
When monochromatic radiation of intensity $I$ falls on a metal surface, the number of photoelectrons and their maximum kinetic energy are $N$ and $K$ respectively. If the intensity of radiation is $2I$, the number of emitted electrons and their maximum kinetic energy are respectively
A 1$\mu$ $A$ beam of protons with a cross-sectional area of $0.5$ sq. mm is moving with a velocity of $3 \times {10^4}m{s^{ - 1}}$. Then charge density of beam is
A totally reflecting small plane mirror placed horizontally faces a parallel beam of light as hown in figure. The mass of mirror is $20\, gm$. Assume that there is no absorption in the lens and that $30\%$ of the light emitted by the source goes through the lens. Find the power of the source needed to support the weight of the mirror ............... $MW$ (take $g = 10\, m/s^2$) :-
A photon falls through a height of $1 \,km$ through the earth's gravitational field. To calculate the change in its frequency, take its mass to be $h v / c^{2}$. The fractional change in frequency $v$ is close to