NALMCO Certified Apprentice Lighting Technician (CALT) Practice Exam

If an HID lamp bulb is phosphor-coated, the lamp generally has better ____ than clear lamp bulbs.

1. Color qualities

2. Efficiencies

3. Service life

4. Voltage ratings

The correct answer is: Color qualities

The correct answer is that an HID lamp bulb that is phosphor-coated generally has better color qualities than clear lamp bulbs. Phosphor coating enhances the overall color rendering of the light output. This is because the phosphors convert some of the shorter-wavelength light produced by the arc discharge into longer wavelengths, resulting in a more balanced and natural appearance of colors. This improved color quality is particularly important in applications where accurate color perception is vital, such as in retail or art galleries. In contrast, while clear lamp bulbs may offer some efficiency and acceptable service life, they do not provide the same enhanced quality of light. Clear bulbs might be more efficient in terms of luminous efficacy, but they do not approach the improved color qualities that phosphor-coated bulbs deliver, which affects the visual experience. Additionally, voltage ratings are typically standard across most HID bulbs and do not relate to the benefits of phosphor coatings.