A $200\, W$ sodium street lamp emits yellow light of wavelength $0.6\, \mu m$. Assuming it to be $25\%$ efficient in converting electrical energy to light, the number of photon of yellow light it emits per second is
$1.5 \times 10^{20}$
$62 \times 10^{20}$
$3 \times 10^{19}$
$6 \times 10^{18}$
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. ........... $MeV$
What is photoelectron ?
If the momentum of a photon is $p$, then its frequency is
Where $m$ is the rest mass of the photon
Light of wavelength $5000\,\,\mathop A\limits^o $ falling on a sensitive surface. If the surface has received $10^{-7}\,J$ of energy, then the number of photons falling on the surface will be
According to photon theory of light which of the following physical quantities associated with a photon do not/does not change as it collides with an electron in vacuum