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.

Options

A. `0.148 m`
B. `0.2 m`
C. `0.25 m`
D. `0.3 m`

Answer

A

Explanation

`E=(hc)/lambda=6.9eV, K.E_(max)=4.9eV`
`Bqv=(mv^(2))/r rArr Bq=P/r rArr Bq=sqrt(2KEm)/r`
`therefore K.E_(max)=(B^(2)q^(2)r^(2))/(2m),r=0.148m`