Light of wavelength 1800 `Å` ejects photoelectrons from a plate of a metal whose work functions is 2 eV. If a uniform magnetic field of `5xx10^(-5)` tesla is applied parallel to plate, what would be the radius of the path followed by electrons ejected normally from the plate with maximum energy.

Explanation

If `v_("max")` is the speed of the fastest electron emitted from them metal suface then
`(hc)/(lamda)=W_(0)+1/2mv_("max")^(2)`
`((6.63xx10^(-34))xx(3xx10^(8)))/((180xx10^(-9)))`
`=2xx(1.6xx10^(-19))=1/2(9.1xx10^(-31))v_("max")^(2)`
`:.v=1.31xx10^(6)m//s`
The radius of the electron is given by
`r=(mv)/(qB)=((9.1xx10^(-31))xx(1.31xx10^(6)))/((1.6xx10^(-19))xx(5xx10^(-9)))`
`=0.149m`