Light appears on a television screen when an electron beam hits a surface covered with what?

• A. Reflectors
• B. Fluorescent dyes
• C. Phosphors
• D. Metals

Answer: (C)

When an electron beam hits a surface covered with phosphors, light is emitted as a result of the interaction between the electrons and the phosphorescent material. Phosphors are substances that exhibit the phenomenon of luminescence, which means they can absorb energy and re-emit it as visible light.

In the context of a television screen, the electron beam strikes the phosphor-coated screen, energizing the phosphors. This energy excites the electrons within the phosphor material, causing them to jump to a higher energy level. When these electrons return to their ground state, they release energy in the form of light. This process is fundamental to the operation of cathode-ray tube (CRT) televisions and is a principle that underpins how images are displayed on the screen.

Reflectors, fluorescent dyes, and metals do not have the same luminescent properties as phosphors. Reflectors are primarily used to direct light rather than emit it, while fluorescent dyes require specific conditions such as UV light for excitation. Metals reflect light but do not emit light in the same manner as phosphors when struck by an electron beam.