$A$ $160 \,W$ light source is radiating light of wavelength $6200 \,\mathring A$ uniformly in all directions. The photon flux at a distance of $1.8 \,m$ is of the order of .......... $m^{-2} s^{-1}$ (Planck's constant $= 6.63 \times 10^{-34} \,J \cdot s$)

What is the momentum of a photon with a frequency of $10^9 \ Hz$?

Specific heat of water is $4.2 \, J/g^{\circ}C$. If light of frequency $3 \times 10^9 \, Hz$ is used to heat $400 \, g$ of water from $20^{\circ}C$ to $40^{\circ}C$,the number of photons needed will be:

If $c$ is the velocity of light in free space,the correct statements about photon among the following are:
$A$. The energy of a photon is $E=h v$.
$B$. The velocity of a photon is $c$.
$C$. The momentum of a photon,$p=\frac{h v}{c}$.
$D$. In a photon-electron collision,both total energy and total momentum are conserved.
$E$. Photon possesses positive charge.
Choose the correct answer from the options given below:

$A$ $200\, W$ 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 photons of yellow light it emits per second is:

The rest energy of an electron is $0.511 \, MeV$. The electron is accelerated from rest to a velocity $0.5 \, c$. The change in its energy will be ............ $MeV$.