$A$ monochromatic beam of light of wavelength $400\,nm$ is incident normally upon a photosensitive surface ($25\%$ reflects and the rest is absorbed). This produces a radiation pressure of $5 \times 10^{-7}\,N/m^2$ on the surface. If $0.1\%$ of the incident photons produce photoelectrons,the corresponding saturation current will be $\dots \mu A$. (Consider the area of the photosensitive surface $= 5\,cm^2$)

Which of the following statements is correct regarding the photoelectric effect?

$A$ photocell is illuminated by a small bright source placed $d \; m$ away. When the same source of light is placed $\frac{d}{2} \; m$ away,the number of electrons emitted by the photocathode would

Describe Hallwach's and Lenard's observations regarding the photoelectric effect in short.

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A :$ In photoelectric effect,on increasing the intensity of incident light,the stopping potential increases.
Reason $R :$ Increase in intensity of light increases the rate of photoelectrons emitted,provided the frequency of incident light is greater than threshold frequency.
In the light of the above statements,choose the correct answer from the options given below:

The number of photoelectrons emitted varies with which physical quantity?