Which of the following is a commonly used light source in modern street light installations?

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Answer 1

High-Pressure Sodium (HPS) lamps

A high-pressure sodium vapor lamp is a gas-discharge lamp that uses excited sodium to produce light. It is highly efficient and has a long lifespan.
High-Pressure Sodium (HPS) lamps are widely used in modern street lighting systems due to their high luminous efficiency (more lumens per watt), long lifespan, reasonable energy efficiency, and good performance in outdoor environments.
They produce a yellow-orange light and are more efficient and durable than incandescent or fluorescent lamps. While LEDs are increasingly replacing HPS in newer installations due to better efficiency and controllability, HPS lamps still dominate many existing street lighting systems.

Fluorescent lamps

A fluorescent lamp is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light.
In fluorescent lamps, the discharge through the vapor produces UV waves, which causes the phosphor coating on the inside of the bulb to glow.
A fluorescent lamp converts electrical energy into useful light much more efficiently than an incandescent lamp.
The typical luminous efficiency of fluorescent lighting systems is 50-100 lumens per watt, several times the efficacy of incandescent bulbs with comparable light output.

Incandescent lamps

An incandescent lamp is an electric light with a wire filament heated until it glows.
The filament is enclosed in a glass bulb with a vacuum or inert gas to protect the filament from oxidation.
They require no external regulating equipment, have low manufacturing costs, and work equally well on either alternating current or direct current.
As a result, the incandescent bulb became widely used in household and commercial lighting.

Metal halide lamps

A metal-halide lamp is an electrical lamp that produces light by an electric arc through a gaseous mixture of vaporized mercury and metal halides.
Metal-halide lamps have a high luminous efficacy of around 75–100 lumens per watt, which is about twice that of mercury vapor lights and 3 to 5 times that of incandescent lights, and produce intense white light.