A radiation of energy $'E'$ falls normally on a perfectly reflecting surface. The momentum transferred to the surface is $( C =$ Velocity of light $)$
$\frac{E}{{C\;}}$
$\;\frac{{2E}}{C}$
$\;\frac{{2E}}{{{C^2}}}$
$\;\frac{E}{{{C^2}}}$
When an inert gas is filled in the place vacuum in a photo cell, then
A photon in motion has a mass
A radio transmitter operates at a frequency of $880 \,kHz$ and a power of $10\,kW$. The number of photons emitted per second are
A parallel beam of light of wavelength $900\,nm$ and intensity $100\,Wm ^{-2}$ is incident on a surface perpendicular to the beam. Tire number of photons crossing $1\,cm ^{2}$ area perpendicular to the beam in one second is :
In an accelerator experiment on high-energy collisions of electrons with positrons, a certain event is interpreted as annihilation of an electron-positron pair of total energy $10.2\; BeV$ into two $\gamma$ -rays of equal energy. What is the wavelength associated with each $\gamma$ -ray? $\left(1\; BeV =10^{9}\; eV \right)$