A monochromatic beam of light of wavelength $400\,nm$ incident normally upon a photosensitive surface ($25\%$ reflects and rest absorbs), produces a pressure of $5 \times 10^{-7}\,Nm^{-2}$ on it. If $0.1\%$ of the incident photons produce electrons then corresponding saturation current will be…………..$\mu A$ (consider area of photosensitive surface $= 5\,cm^2$)

The energy equivalent to $1\,mg$ of matter in $MeV$ is

Write characteristic of photon or How photon of electromagnetic radiation can be represented ? 

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

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?