Answer:
Electric field magnitude
E = K/qd
Where
K = kinetic energy of electron
d = electron distance
q = charge
Step-by-step explanation:
Given the relationship between workdone and energy
Work-energy theorem:
Net workdone = Energy change
W = ∆E
In this case
W = ∆K.E
And,
∆K.E = K(final) - K(initial)
To stop the kinetic energy | K(final) = 0
K(initial) = K (given)
∆K.E = 0 - K = -K
Let the electric force on the electron has magnitude F.
And
W = -Fd = ∆K.E = -K
-Fd = -K
F = K/d .....1
The magnitude of the electric field E that can stop these electron in a distance d:
E = F/q ......2
Where q is the charge on electron.
substituting equation 1 to 2
E = (K/d)/q = K/qd
E = K/qd