The energy of a photon of visible light with the maximum wavelength in $eV$ is approximately .......

Which of the following has a mass closest in value to that of the positron? $(1\;a.m.u = 931\;MeV)$

Two sources of light emit $X$-rays of wavelength $1 \ nm$ and visible light of wavelength $500 \ nm$,respectively. Both sources emit light of the same power $200 \ W$. The ratio of the number of photons emitted per second by the $X$-ray source to the number of photons emitted per second by the visible light source is:

Monochromatic light of wavelength $3000 \, \mathring{A}$ is incident on a surface of area $4 \, cm^2$. If the intensity of light is $150 \, mW/m^2$, then the rate at which photons strike the target is:

$A$ photon creates an electron-positron pair with equal kinetic energy. If the kinetic energy of each particle is $0.29 \ MeV$,the energy of the photon must be .......... $MeV$.

According to the photon theory of light,which of the following physical quantities associated with a photon does not change as it collides with an electron in a vacuum?