What is a photoelectron?

Give an outline of the experimental study of the photoelectric effect.

$A$ photosensitive material is at $9\,m$ to the left of the origin and the source of light is at $7\,m$ to the right of the origin along the $x$-axis. The photosensitive material and the source of light start from rest and move,respectively,with $8\widehat{i}\,m/s$ and $4\widehat{i}\,m/s$. The ratio of intensities at $t = 0$ to $t = 3\,s$ as received by the photosensitive material is:

Which of the following graphs represents the variation of photoelectric current with the property of light shown on the $x-$axis?

Assertion $(A) :-$ The photoelectrons produced by a monochromatic light beam incident on a metal surface have a spread in their kinetic energies.
Reason $(R) :-$ The work function of the metal varies as a function of depth from the surface.

The graph shows the variation of photocurrent with anode potential for four different radiations. Let $I_a, I_b, I_c$ and $I_d$ be the intensities and $f_a, f_b, f_c$ and $f_d$ be the frequencies for the curves $a, b, c$ and $d$ respectively,then