Light of wavelength 180 nm ejects photoelectrons from a plate of metal whose work - function is 2 eV. If a uniform magnetic field of `5xx10^(-5)` T be applied parallel to the plate, what would be the radius of the path followed by electrons ejected normally from the plate with maximum energy.

Explanation

Maximum kinetic energy of electrons
`K_(max)=(1)/(2)mv_(max)^(2)=(hc)/(lamda)-W`
`K_(max)=((6.62xx10^(-34))(3xx10^(8)))/((180xx10^(-9)))-(2xx1.6xx10^(19))`
`=7.8xx10^(-19)J`
`v_(max)=sqrt(((2K_(max)))/(m))=sqrt(((2xx(7.8xx10^(-19)))/(9.1xx10^(-31))))`
`=1.3xx10^(6)`
Now, `Bev_(max)=(mv_(max)^2)/(r)`
`r=(mv_(max))/(Be)=((9.1xx10^(31))(1.3xx10^(6)))/((5xx10^(-5))(1.6xx10^(-19)))`
`=0.148m`