Question

The kinetic energy associated with an electron of velocity 10^6 m/s
(a) 0.28 eV
(b) 2.8eV
(c) 0.56 eV
(d) 5.6ev​

Answer 1

Given : e=1.6×10−19C, c=3×108m/s

             ϕ=4.2eV, h=6.63×10−34J.s, VS=3V

             ϕ=4.2×1.6×10−19J

                 =6.72×10−19J

(a) Threshold wavelength =λ0=ϕhc

                                          =6.72×10−196.63×10−34×3×108

                                          =2.960×10