NALMCO Certified Apprentice Lighting Technician (CALT) Practice Exam

Rated lamp life indicates when what percentage of lamps is expected to fail?

1. 20%

2. 50%

3. 75%

4. 100%

The correct answer is: 50%

Rated lamp life refers to the period during which a specific percentage of lamps are expected to function properly before reaching failure. When it is indicated that 50% of lamps are expected to fail, it means that after the rated lamp life is achieved, approximately half of the lamps will have burnt out while the other half are expected to continue working. This metric is crucial in lighting design and maintenance planning as it helps in predicting when replacements will be necessary and assists users in determining cost-effectiveness over time. By understanding rated lamp life, lighting technicians and facility managers can implement proper schedules for lamp replacements and manage inventory more effectively. In contrast, the other percentages reflect different performance expectations. For example, if a rating indicated 75% or 100% failure, it would suggest a very different lifespan expectation. Therefore, the 50% failure point is foundational for understanding average lifespan and reliability across a wide range of lighting applications.