Explanation :
From the given figure, point P is located in the electric field between two oppositely charged parallel plates.
If an electron is placed at point P, it will repel by the negative plate of the capacitor and will move towards positive plate i.e. from the negative plate to positive plate.
Similarly, when a proton is placed at point P, it will attract towards the negative plate i.e. the direction of the proton will be from positive plate to negative plate.
We know that the electrostatic force is inversely proportional to the square of the distance.
So, the electrostatic force on a proton placed at point P has a greater magnitude and the opposite direction".