Practice Test Geeks(CLC) Certified Lighting Consultant Practice Test
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Light Source Technology & LEDs Flashcards

7 cards from real CLC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Light Source Technology & LEDs flashcards as text

  1. What is the primary cause of 'color shift' in LED luminaires over their rated life?

    Answer: Phosphor degradation and silicone yellowing in the package

    Phosphor degradation and silicone encapsulant yellowing caused by heat and UV exposure are the primary drivers of chromaticity shift in LED products over time.

  2. Which LED metric specifically describes the ratio of luminous flux emitted in the forward hemisphere versus total fixture input power?

    Answer: Luminaire efficacy rating (LER)

    LER (Luminaire Efficacy Rating) accounts for luminaire optical losses, driver losses, and thermal losses to express delivered lumens per input watt.

  3. A TRIAC (phase-cut) dimmer causes visible flicker with an LED driver primarily because:

    Answer: The LED driver cannot regulate current smoothly from the chopped AC waveform

    TRIAC dimmers chop the AC waveform; many LED drivers struggle to filter this irregular input and produce stable DC current, causing flicker or instability.

  4. What does 'R9' value indicate in a CRI report for an LED source?

    Answer: The rendering of saturated red (test color sample 9)

    R9 is the CRI score for test color sample 9, which is a saturated red; a high R9 (>50) is critical for applications like food retail or skin tones.

  5. Which thermal parameter is used to compare the heat dissipation capability of different LED packages from junction to the circuit board?

    Answer: Thermal resistance junction-to-solder point (Rth j-s)

    Rth j-s (junction-to-solder-point thermal resistance) quantifies how efficiently heat moves from the LED die to the board, enabling comparison between packages.

  6. An LED with a MacAdam ellipse rating of '3-step SDCM' means:

    Answer: Color variation between units is within 3 standard deviations of the reference point on the CIE diagram

    SDCM (Standard Deviation of Color Matching) ellipses define the color tolerance zone; a 3-step rating means most observers cannot detect color differences within the batch.

  7. What is the function of a Zener diode often included in an LED circuit or module?

    Answer: To act as electrostatic discharge (ESD) protection for the LED junction

    Zener diodes placed in parallel with LEDs clamp voltage transients and protect the sensitive LED junction from ESD damage.