A low-pressure gas discharge tube emits which of the following?

• A. Continuous white light
• B. Discrete spectral lines characteristic of the gas
• C. Only infrared radiation
• D. No electromagnetic radiation

Answer: (B)

Verified step by step guidance

1. Understand that a low-pressure gas discharge tube contains gas atoms excited by an electric current, causing electrons in the atoms to move to higher energy levels.
2. Recall that when these excited electrons return to lower energy levels, they emit photons with specific energies corresponding to the differences between energy levels.
3. Recognize that these emitted photons produce discrete spectral lines, which are unique to the type of gas present in the tube, rather than a continuous spectrum.
4. Contrast this with continuous white light, which is emitted by solids or dense gases where many overlapping transitions occur, producing a continuous range of wavelengths.
5. Conclude that the emission from a low-pressure gas discharge tube is characterized by discrete spectral lines specific to the gas, not continuous light or only infrared radiation.