Question

Cathode rays are made to pass between the poles of a magnet perpendicular to axis. The effect of the magnetic field is

• A. to increase the velocity of rays
• B. to deflect them towards the north pole
• C. to deflect them toward the south pole
• D. to deflect them upward above the plane of paper

Answer 1

Answer: (D)

to deflect them upward above the plane of paper

The force on cathode rays which constitutes electron particles, due to perpendicular Magnetic field is $\overrightarrow{F}-e(\overrightarrow{v}\times \overrightarrow{B})$ which is perpendicular to the plane of velocity and Magnetic field.

So cathode rays are deflected upward above the plane of paper.