Answer:
3 cm
Explanation:
According to the question,
.
.
.
Now the approximate slit's image width is equal to width of central maxima.
And width of central maxima is twice the width from center to first maxima
So,
.
Substitute all the variable in above equation.
.
.
The current will be divided by 2
So that the oil drop stays suspended.
at the point where it is stationary, its weight and the force on it due to the field are equal . so you can work out any detail you need