A radio transmitter radiates $1 kW$ power at a wavelength $198.6 $ metres. How many photons does it emit per second
${10^{10}}$
${10^{20}}$
${10^{30}}$
${10^{40}}$
Monochromatic light of frequency $6.0 \times 10^{14} \;Hz$ is produced by a laser. The power emitted is $2.0 \times 10^{-3} \;W$.
$(a)$ What is the energy of a photon in the light beam?
$(b)$ How many photons per second, on an average, are emitted by the source?
In photoelectric effect if the intensity of light is doubled then maximum kinetic energy of photoelectrons will become
Rest mass energy of an electron is $0.51\ MeV.$ If this electron is moving with a velocity $0.8\ c$ (where $c$ is velocity of light in vacuum), then kinetic energy of the electron should be. ........... $MeV$
Energy of photon whose frequency is ${10^{12}}MHz,$ will be