CLD Lighting Fundamentals 5

Question 1

What is 'exitance' (formerly called emittance) in photometry?

Accepted Answer

The luminous flux per unit area leaving a surface

Answer

Luminous exitance (M) is the total luminous flux emitted or reflected per unit area of a surface, measured in lumens per square meter (lm/m²).

Question 2

A designer wants to reduce the 'room cavity ratio' (RCR). Which change would accomplish this?

Accepted Answer

Lowering the ceiling height while keeping the room dimensions the same

Answer

RCR = 5 × h × (L + W) / (L × W), so decreasing room cavity height (h) directly reduces the RCR value.

Question 3

What is the purpose of a 'cutoff' classification in roadway luminaire photometry?

Accepted Answer

To define the maximum allowable uplight and glare from the luminaire

Answer

Cutoff classifications (full cutoff, cutoff, semicutoff, non-cutoff) define limits on luminaire intensity above the horizontal to control light trespass, sky glow, and glare.

Question 4

Which factor does NOT influence the maintained illuminance level in the zonal cavity method?

Accepted Answer

Lamp base type (e.g., medium vs. mogul)

Answer

Lamp base type is a mechanical feature affecting installation compatibility but has no influence on the photometric calculations in the zonal cavity method.

Question 5

What is 'flicker' in LED lighting, and why is it a concern?

Accepted Answer

Rapid, periodic variation in light output, which can cause visual fatigue or health issues

Answer

Flicker is the rapid, cyclic variation in light output — often at 100–120 Hz — that can cause eye strain, headaches, or trigger photosensitive conditions.

(CLD) Certified Lighting Designer Practice Test

(CLD) Certified Lighting Designer Practice Test

CLD Lighting Fundamentals 5