1. How did Roentgen discover X-rays?
Answer: While experimenting with a glass tube from which the air had been pumped, Roentgen happened to pass an electric current through the tube. Nearby was a screen coated with Barium Platinocyanide. Suddenly he noticed that the screen was glowing with a greenish blue light. After experimenting with this radiation, coming from the evacuated glass tube Roentgen found that this radiation could pass through substances of varying densities placed between the tube and t