NALMCO Certified Apprentice Lighting Technician (CALT) Practice Exam

Which type of HID lamp is known for its excellent energy efficiency and long life?

1. High-pressure sodium

2. Metal halide

3. Low-pressure sodium

4. Mercury vapor

The correct answer is: Low-pressure sodium

The type of HID lamp recognized for its excellent energy efficiency and long life is the low-pressure sodium lamp. These lamps are known for their ability to produce a significant amount of light relative to the energy consumed, making them highly efficient. Additionally, low-pressure sodium lamps have an extensive lifespan, often exceeding that of many other lamp types, which reduces the frequency of replacements and maintenance costs. These lamps operate by producing light through the excitation of sodium vapor, resulting in a very distinct yellow color. While high-pressure sodium and metal halide lamps also have their advantages, particularly in terms of light quality and spectral variety, low-pressure sodium is unmatched in energy efficiency and longevity, which makes it an ideal solution for applications requiring extended operational periods with lower energy usage. It's important to note that mercury vapor lamps, while historically significant, do not match the efficiency and lifespan of low-pressure sodium lamps, making them less favorable in many recent applications.