Between two parallel plates an electron escapes from the pos

Between two parallel plates, an electron escapes from the positively charged plate at v10s towards the negatively charged plate. It stops just before reaching the negatively charged plate. What is the electric field and the potential difference between the plates if the separation between the plates is 20 cm

Solution

work done by the potential differnce = change in kinetic energy

q*dV = 0.5*m*vi^2

q is the charge on electron = 1.6*10^-19 C

dV is the potential difference

m is the mass of electron = 9.11*10^-31 kg

vi = 10^7 m/s

then

q*dV = 0.5*m*vi^2

1.6*10^-19*dV = 0.5*9.11*10^-31*(10^7)^2

dV = 284.68 V

electric field is E = dV/d = 284.68/0.2 = 1423.4 V/m