Which type of lamp uses sodium gas to produce light?

The correct choice is the high-pressure sodium lamp, which utilizes sodium gas in its operation to produce light. When an electric current is passed through the sodium gas at high pressure, it emits a bright yellow-orange light. This type of lamp is notable for its efficiency and is commonly used in street lighting and outdoor applications due to its ability to produce a significant amount of light while consuming relatively low energy.

The high-pressure sodium lamp operates on the principle of gas discharge lighting, where the ionized sodium gas luminesces when energized, contributing to its distinctive color and high efficiency. This technology is beneficial in minimizing energy consumption while providing effective illumination.

Other types of lamps like halide lamps, mercury vapor lamps, and incandescent lamps utilize different gases or mechanisms for producing light, making them distinct from high-pressure sodium lamps. Halide lamps contain metal halides and produce a white light; mercury vapor lamps use mercury vapor for light generation but typically emit more bluish hues; and incandescent lamps operate by heating a filament until it glows, without any gas discharge mechanism involved. This highlights the unique characteristics and applications of high-pressure sodium lamps in comparison to the other options.