The material of the cathode in a photocell is changed such that the work function of the surface changes from $W_1$ to $W_2$ $(W_2 > W_1)$. If the photocurrents emitted before and after changing the cathode surface are $I_1$ and $I_2$ respectively,and $hf > W_2$,then:

$10^{-3} \, W$ of $5000 \, \mathring{A}$ light is directed on a photoelectric cell. If the current in the cell is $0.16 \, \mu A$,the percentage of incident photons which produce photoelectrons is .......$\%$

The graph between the intensity of light $(I)$ falling on a metallic plate and the generated photoelectric current $(i)$ is:

$A$ 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:

In the photoelectric effect,the photocurrent:

Define threshold frequency and on which factor does threshold frequency depend?