The graph given in the figure shows the variation of photocurrent $(I)$ with the applied voltage $(V)$ for two different materials and for two different intensities of incident radiation. Which of the following pairs of curves represent the same material?

When the intensity of incident light increases:

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:

For photoelectric emission, tungsten requires light of $2300 \mathring{A}$. If light of $1800 \mathring{A}$ wavelength is incident, then emission:

$A$ 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 number of photo-electrons emitted per second from a metal surface increases when: