Joseph John Thomson

“ Before discussing Wien's experiments it will be convenient to consider the theory of the deflection of a moving electrified particle by a magnetic field. The force acting on the moving particle is at right angles to the magnetic force, at right angles to the direction of motion of the particle and equal to eHvsinΦ, where H is the magnetic force at the particle, v the velocity of the particle, Φ the angle between H and v, and e the charge on the particle. ”

“ Comparing the shape of the shadow with that of the obstacle, it is found that the shadow is very approximately the projection of the outside of the solid on the walls of the tube by lines passing through the hole in the cathode through which the pencil of positive rays emerges. ”

“ Where A depends merely upon the strength of the magnetic field and the distance from the point of projection at which the deflection is measured; it is quite independent of the charge mass, or velocity of the particle. ”