Lighting & Illuminance MCQ's

25 Jun, 2025


1. Which unit is used to measure illuminance?



ANSWER= (C) Lux
Explaination:- Lux is the unit of illuminance and is defined as one lumen per square meter

2.In interior lighting design, the Lumen Method is typically used when:

        There is natural lighting only
ANSWER= (C) The light distribution is uniform
Explaination:- The Lumen Method is best suited for uniformly distributed lighting in regular-shaped spaces.
 


3. Which factor is used in the lumen method to account for dirt and aging?
     
     
     
     
ANSWER= (B) Depreciation factor
Explaination:- The depreciation factor (or maintenance factor) adjusts the design illuminance to account for reduction over time.

 

4. Which type of lighting distribution is ideal for libraries and classrooms?

    Indirect lighting
    Direct lighting
    Semi-indirect lighting
ANSWER= (D) General diffused lighting
Explaination:- Diffused lighting reduces shadows and glare, creating a comfortable reading and learning environment..


5. For emergency lighting, what is the minimum required illuminance as per IS 10905?

     5 lux
     10 lux
     0 lux
     
ANSWER= (A) 5 lux
Explaination:- For escape routes and emergency lighting, IS 10905 mandates a minimum of 5 lux to ensure safe evacuation.


6. Which standard primarily governs interior illumination in India?

     
     
     
     
ANSWER= (B) IS 3646
Explaination:- IS 3646 provides detailed recommendations for the design of lighting systems in buildings.


7. Which of the following has the highest luminous efficacy?

A. Incandescent lamp

B. CFL

C. Metal Halide

D. LED

Answer: D. LED

Explanation: LEDs have the highest luminous efficacy, often exceeding 120 lm/W, compared to other sources.


8. What does “uniformity ratio” refer to in lighting design?

A. Ratio of average to minimum illuminance

B. Ratio of total lumens to floor area

C. Ratio of direct to indirect light

D. Ratio of maintained to initial illuminance

Answer: A. Ratio of average to minimum illuminance

Explanation: Uniformity ensures consistent lighting, avoiding bright and dark patches in a workspace.


9. What is the typical lux level recommended for a residential kitchen area?

A. 100 lux

B. 150 lux

C. 250 lux

D. 300 lux

Answer: D. 300 lux

Explanation: Residential kitchens need around 300 lux for effective food preparation and safety.


10. A drawing room has 4 LED downlights, each rated at 1000 lumens. If the room is 5m x 4m, what is the average illuminance? (Assume 80% utilization and 0.8 maintenance factor)

A. 40 lux

B. 64 lux

C. 128 lux

D. 100 lux

Answer: C. 128 lux

Explanation:

Total lumens = 4 x 1000 = 4000

Effective lumens = 4000 × 0.8 × 0.8 = 2560

Area = 5 × 4 = 20 m²

Illuminance = 2560 / 20 = 128 lux


11. Which lighting technique is used to highlight textured surfaces like stone or brick walls?

A. Diffused lighting

B. Cove lighting

C. Grazing lighting

D. General lighting

Answer: C. Grazing lighting

Explanation: Grazing involves placing lights close to the surface to emphasize texture through shadow and contrast.


12. What is the maximum mounting height for street lighting in residential areas as per Indian norms?

A. 5 m

B. 6 m

C. 8 m

D. 10 m

Answer: B. 6 m

Explanation: As per CPWD norms and municipal guidelines, 6 m is ideal for residential area poles to maintain uniform lighting and reduce glare.


13. In a lighting layout plan, which symbol represents a ceiling-mounted downlight?

A. Circle with cross

B. Triangle

C. Square with a dot

D. Circle with arrow

Answer: A. Circle with cross

Explanation: Common drafting symbol for ceiling downlights is a circle with a cross or dot at center.


14. Which lamp type is most affected by ambient temperature changes?

A. LED

B. Fluorescent

C. Halogen

D. Incandescent

Answer: B. Fluorescent

Explanation: Fluorescent lamps are sensitive to temperature and may not start or perform well in low-temperature environments.


15. When designing task lighting, what is the recommended lux level for drawing or detailed design work?

A. 200 lux

B. 500 lux

C. 750 lux

D. 1000 lux

Answer: D. 1000 lux

Explanation: For precise and visually demanding tasks like drafting, 1000 lux is recommended.


16. In a lighting circuit, what is the standard wire gauge (copper) used for general lighting in Indian homes?

A. 0.5 mm²

B. 1.0 mm²

C. 1.5 mm²

D. 2.5 mm²

Answer: C. 1.5 mm²

Explanation: 1.5 mm² copper wire is commonly used for lighting circuits as per IS 732.


17. According to IS 3646, which factor influences the Coefficient of Utilization (CU)?

A. Type of lamp

B. Mounting height

C. Reflectance of room surfaces

D. Shape of the luminaire

Answer: C. Reflectance of room surfaces

Explanation: CU is affected by surface reflectance, room geometry, and luminaire design, but reflectance has major influence.


18. What does the term “luminous efficacy” refer to?

A. Power factor of lighting

B. Brightness of the source

C. Lumens per watt

D. Lifetime of the lamp

Answer: C. Lumens per watt

Explanation: Luminous efficacy measures how efficiently a light source converts electrical power into visible light.


19. In an LED luminaire, what typically causes a reduction in illuminance over time?

A. Flicker

B. Driver fault

C. Lumen depreciation

D. Power factor drop

Answer: C. Lumen depreciation

Explanation: Over time, the output of LEDs decreases, leading to a drop in illuminance, even if power input remains the same.

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