Answer:
The speed of electron is

Step-by-step explanation:
Given that,
Separation of the plate = 1.20 cm
Suppose the field is
.
If the electron is accelerated from rest near the negative plate and passes through a tiny hole in the positive plate.
What the speed does it leave the hole?
We need to calculate the acceleration
Using formula of electric force



We need to calculate the speed of electron
Using equation of motion


Put the value of acceleration in the formula

Put the value into the formula



Hence, The speed of electron is
