$A$ point source of light is used in an experiment on the photoelectric effect. Which of the following curves best represents the variation of photocurrent $(i)$ with distance $(d)$ of the source from the emitter?

The work functions of Caesium $(Cs)$, Potassium $(K)$, and Sodium $(Na)$ are $2.14\,eV$, $2.30\,eV$, and $2.75\,eV$ respectively. If incident electromagnetic radiation has an incident energy of $2.20\,eV$, which of these photosensitive surfaces may emit photoelectrons?

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:

When yellow light is incident on a surface,no electrons are emitted,while green light can emit them. If red light is incident on the surface,then:

$A$ convex lens of focal length $40 \ cm$ forms an image of an extended source of light on a photoelectric cell. $A$ current $I$ is produced. The lens is replaced by another convex lens having the same diameter but focal length $20 \ cm$. The photoelectric current now is:

The figure shows a plot of photo current versus anode potential for a photo sensitive surface for three different radiations. Which one of the following is a correct statement?