2. Solved Papers
  3. VIT Engineering

VIT Engineering VIT Engineering Solved Paper-2009

  • question_answer
    A photon of energy E ejects a photoelectron from a metal surface whose work function is \[{{W}_{0}}\]. If this electron enters into a uniform magnetic field of induction B in a direction perpendicular to the field and describes a circular path of radius \[r\], then the radius \[r\] is given by, (in the usual notation)

    A)  \[\frac{\sqrt{2m\left( E-{{W}_{0}} \right)}}{eB}\]

    B)  \[\sqrt{2m\left( E-{{W}_{0}} \right)}eB\]

    C)  \[\frac{\sqrt{2e\left( E-{{W}_{0}} \right)}}{mB}\]

    D)  \[\frac{\sqrt{2m\left( E-{{W}_{0}} \right)}}{eB}\] 

    Correct Answer: D

    Solution :

    From Einsteins equation \[E={{W}_{0}}+\frac{1}{2}m{{v}^{2}}\] \[\sqrt{\frac{2(E-{{W}_{0}})}{m}}=v\] or A charged particle placed in uniform magnetic field experience a force \[F=\frac{m{{v}^{2}}}{r}\] or \[evB=\frac{m{{v}^{2}}}{r}\] or \[r=\frac{mv}{eB}\] or \[r=\frac{m\sqrt{\frac{2(E-{{W}_{0}})}{m}}}{eB}\] \[\Rightarrow \] \[r=\frac{\sqrt{2m(E-{{W}_{0}})}}{eB}\]  


You need to login to perform this action.
You will be redirected in 3 sec spinner