$A$ photocell employs the photoelectric effect to convert

Explain Hertz's observation in short.

Energy conversion in a photoelectric cell takes place from

If the intensity of incident light is increased in $PEE$,then which of the following is true?

From the photoelectric effect experiment, the following observations are made. Identify which of these are correct:
$A.$ The stopping potential depends only on the work function of the metal.
$B.$ The saturation current increases as the intensity of incident light increases.
$C.$ The maximum kinetic energy of a photoelectron depends on the intensity of the incident light.
$D.$ The photoelectric effect can be explained using the wave theory of light.
Choose the correct answer from the options given below:

The cathode of a photoelectric cell is changed such that the work function changes from $W_1$ to $W_2$ $(W_2 > W_1)$. If the current before and after change are $I_1$ and $I_2$,all other conditions remaining unchanged,then (assuming $h\nu > W_2$):