When a monochromatic point source of light is at a distance of $0.2 \mathrm{m}$ from a photoelectric cell, the cutoff voltage and the saturation current are respectively $0.6 \mathrm{V}$ and $18 \mathrm{mA}$. If the same source is placed $0.6 \mathrm{m}$ away from the cell, then : 

The work function of a certain metal is $\frac{hc}{{\lambda }_0}$. When a monochromatic light of wavelength $\lambda <{\lambda }_0$ is incident such that the plate gains a total power $P$. If the efficiency of photoelectric emission is $\mathrm{\eta }\%$ and all the emitted photoelectrons are captured by a hollow conducting sphere of radius $R$ already charged to potential $V$, then neglecting any interaction between plate and the sphere, expression of potential of the sphere at time $t$ is,

$(\mathrm{e}=1.6\times {10}^{–19}\mathrm{C})$

The radiation force experienced by body exposed to radiation of intensity $I$, assuming surface of body to be perfectly absorbing is :

In an experiment on the photoelectric effect, the separation between the emitter and the collector plates is $10 \mathrm{cm}$. Plates are connected through an ammeter without any cell. A Magnetic field $B$ exists parallel to the plates. The work function of the emitter is $2.39 \mathrm{eV}$ and, the light of wavelengths between $400 \mathrm{nm}$ and $600 \mathrm{nm}$ is incident on it. If the minimum value of $B$ for which the current registered by the ammeter is zero is $n\times {10}^{–6} \mathrm{T}$. Then find out the value of $n$ (Neglect any effect of space charge). (Assume emission of photoelectron to be randomly every possible direction)