Question bank/JEE Main/Physics

Radiation, with wavelength falls on a metal surface to
produce photoelectrons. The electronsare made to enter a uniform
magnetic field of $3 \times 10^{- 4}$T. If the radius of the largest
circular pathfollowed by the electrons is 10 mm, the work function of
the metal is close to

A1.8 eVB0.8 eVC1.6 eVD1.1 eV

Show answer and solution▾

${KE}_{\max} = E - \phi$
$= \frac{12400}{\lambda(inÅ)} - \phi$ (in eV)
$r = \frac{\sqrt{2mKE}}{eB}$
$KE_{\max} = \frac{r^{2}e^{2}B^{2}}{2m}$ (in J)
$= \frac{r^{2}eB^{2}}{2m}$ (in eV)

Source: Grass-G / P-19 Physics paper 28 Nov Fourth.docx