gave an impression through the black paper.
If a particle of mass m, charge e, and velocity u, is projected normally to an electric field of strength X, the acceleration α is in the direction of the field, and is given by
Since the particle moves with a constant acceleration parallel to the field, the path of the particle is the same as that of a body projected horizontally from a height with a constant velocity and acted on by gravity. The path of the particle is thus a parabola, whose axis is parallel to the field and whose apex is at the point where the particle enters the electric field. The linear deviation d1 of the ray parallel to the field after traversing a distance l is given by
On leaving the electric field, the particle travels in the direction of the tangent to the path at that point. If θ is the angular deviation of the path at that point
The photographic plate was at a distance h above the extremity of the field. Thus the particles struck the plate at a distance d2 from the original path given by
In the experimental arrangement the values were
If the radius R of