An electron beam accelerated from rest through a potential difference of 5000 V in vaccum is allowed to impinge on a surface normally. The incident current is 50 ~A and if the electron comes to rest on striking the surface, the force on it is

Step-by-step solution

Energy = 1 2 m v^2=5000 eV aligned & =5000 1.6 10⁻¹⁹ ~J m v₂ & = 2 5000 (1.6 10⁻¹⁹ ) m & =4 10⁻⁸ m aligned Number of electrons striking per second is aligned & n= q e = I t e = 50 10⁻⁶ 1 1.6 10⁻¹⁹ n & =31.25 10¹³ aligned Force = Change of momentum per second aligned & =n(m v)=31.25 10¹³ 4 10⁻⁸ m & =125 10^5 9.1 10⁻³¹ =1.1924 10⁻⁸ ~N aligned