Final answer:
Low-Pressure Sodium Lamps produce a distinctive yellow light through the excitation of sodium vapor, which is effective in penetrating fog and commonly used for street lighting.
Step-by-step explanation:
Low-Pressure Sodium Lamps are a type of gas-discharge lamp that uses sodium in an excited state to produce light at a characteristic wavelength, specifically in the sodium emission spectrum. When an electrical discharge passes through sodium vapor, it produces a bright yellow color.
This particular type of lighting is effective for use in outdoor lighting such as street lights because sodium vapor penetrates fog efficiently, allowing the yellow light to be scattered less by the fog compared to white light. The narrow emission spectrum of low-pressure sodium lamps makes them quite efficient and recognizable by their distinctive monochromatic yellow glow.