In a photocell bichromatic light of wavelength 2475 $\stackrel{\mathrm{o}}{\mathrm{A}}$ and 6000 $\stackrel{\mathrm{o}}{\mathrm{A}}$ are incident on cathode whose work function is 4.8 eV. If a uniform magnetic field of $3 x {10}^{-5}$ Tesla exists parallel to the plate, the radius of the path describe by the photoelectron will be (mass of electron = $9 x {10}^{-31}$ kg)

Energy of photons corresponding to light of wave

$\begin{array}{l}\mathrm{length}{\mathrm{\lambda }}_1=2475\stackrel{\mathrm{o}}{\mathrm{A}}\mathrm{is}{\mathrm{E}}_1=\frac{12375}{2475}=5\mathrm{eV}\\ \mathrm{and}\mathrm{that}\mathrm{corresponding}\mathrm{to}{\mathrm{\lambda }}_2=6000\stackrel{\mathrm{o}}{\mathrm{A}}\mathrm{is}\\ {\mathrm{E}}_2=\frac{12375}{6000}=2.06\mathrm{eV}\\ \mathrm{As}{\mathrm{E}}_2<{\mathrm{W}}_{\mathrm{o}}\mathrm{and}{\mathrm{E}}_1>{\mathrm{W}}_{\mathrm{o}}\\ \mathrm{Photoelectric}\mathrm{emission}\mathrm{is}\mathrm{possible}\mathrm{with}{\mathrm{\lambda }}_1\mathrm{only}.\\ \mathrm{Maximum}\mathrm{kinetic}\mathrm{energy}\mathrm{of}\mathrm{emitted}\mathrm{photoelectrons}\mathrm{K}=\mathrm{E}-{\mathrm{W}}_{\mathrm{o}}=5-4.8=0.28\mathrm{eV}.\\ \mathrm{Photo}\mathrm{electrons}\mathrm{experiences}\mathrm{magnetic}\mathrm{force}\mathrm{and}\mathrm{move}\mathrm{along}\mathrm{a}\mathrm{circular}\mathrm{path}\mathrm{of}\mathrm{radius}\\ \mathrm{r}=\frac{\sqrt{2\mathrm{mk}}}{\mathrm{QB}}\frac{\sqrt{2\times 9\times {10}^{-31}\times 0.2\times 1.6\times {10}^{-19}}}{1.6\times {10}^{-19}\times 3\times {10}^{-5}}=0.05\mathrm{m}=5\mathrm{cm}\end{array}$