Question

The nature of electron beams moving with uniform velocity in the same direction will be:

• A. converging
• B. diverging
• C. parallel
• D. none of these

Hint:

Like charges repel, so electron beams tend to diverge unless focused by external forces.

Answer 1

The Correct Option is B

Electrons are negatively charged particles, and according to Coulomb’s law, like charges repel each other with a force that is inversely proportional to the square of the distance between them. This fundamental electrostatic repulsion causes electrons within a beam to push away from one another. When multiple electron beams are moving parallel to each other with uniform velocity, each electron in one beam experiences repulsive forces from the electrons in the neighboring beams. These forces act perpendicular to the direction of motion and cause the beams to exert a lateral push against each other. Because the electrons are all moving in the same direction with approximately the same velocity, the mutual repulsion is not balanced by any attractive forces. This leads to a gradual spreading or divergence of the electron beams as they travel. In practical applications, such as cathode ray tubes or electron microscopes, this effect limits the ability to keep electron beams narrowly focused over long distances. Engineers often use magnetic or electrostatic lenses to counteract this divergence and maintain beam coherence. In summary, the tendency of electron beams to diverge when moving parallel with uniform velocity arises from the mutual electrostatic repulsion between electrons carrying like negative charges, which pushes the beams apart laterally as they propagate.