An electron with (rest mass $m_{0}$ ) moves with a speed of $0.8 c$. Its mass when it moves with this speed is

The rest mass of the photon is

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 sensor is exposed for time $t$ to a lamp of power $P$ placed at a distance $l$. The sensor has a circular opening that is $4d$ in diameter. Assuming all energy of the lamp is given off as light, the number of photons entering the sensor if the wavelength of light is $\lambda $ is $(l >> d)$

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

In photoelectric effect, if a weak intensity radiation instead of strong intensity of suitable frequency is used then