How did Goldstein modify the cathode-ray tube for canal rays?

Goldstein improved the traditional cathode-ray tube by introducing a perforated cathode—a negative electrode with small holes. This design let him observe new rays moving in the opposite direction of the cathode rays, passing through the holes. He called these canal rays.

Modifications and Observations

1. Perforated Cathode: Goldstein replaced the usual solid cathode with one that had small holes or “canals.” These holes allowed certain rays to pass through the cathode.

2. High Voltage: A high electrical voltage was applied across the electrodes to ionize the gas inside the partially evacuated tube.

3. Observation of Canal Rays: Goldstein noticed faint, glowing rays that moved away from the anode and passed through the holes in the cathode—unlike normal cathode rays, which travel from the cathode to the anode.

4. Properties of Canal Rays: These rays were deflected by electric and magnetic fields in a direction opposite to cathode rays, showing that they consisted of positively charged particles.