The Magic of Colors in Gas Discharge Tubes

Why does a gas discharge tube (e.g., a neon light) have a certain color?

A. Temperature of the gas

B. Pressure of the gas

C. Composition of the gas

D. Voltage across the tube

Final answer:

The correct option is C. Composition of the gas.

The color of a gas discharge tube is determined by the composition of the gas inside the tube. Neon gas produces a red color, while other gases or mixtures can produce different colors.

Explanation: The color of a gas discharge tube, such as a neon light, is determined by the composition of the gas inside the tube. Temperature, pressure, and voltage do not directly determine the color.

Different gases or mixtures of gases produce different colors of light when an electric current is passed through them. For example, the familiar red color of neon signs is due to the emission spectrum of neon gas. Mixing argon or mercury vapor with neon or using glass tubes of a special color can also change the color of the light.

The other factors listed, such as the temperature of the gas, pressure of the gas, and voltage across the tube, may affect the behavior of the gas discharge tube but do not directly determine its color.