Illumination and Lighting Engineering MCQs 2026

Luminous flux is measured in

1. Alumen (lm)✓
2. Blux only without area✓
3. Ccandela-second only✓
4. Dwatt✓

Light pollution from poor street lighting design is reduced by

1. Afull cut-off optics and curfew dimming where permitted✓
2. Baiming luminaires at sky✓
3. Cusing only bare lamps on low poles✓
4. Dmaximizing uplight for ambiance✓

Series street lighting (historical) used

1. Aparallel household wiring only✓
2. Bonly DC traction feeder✓
3. Cconstant current series circuit with isolation transformers✓
4. Donly open-delta transformer without lamps✓

International practice for road lighting classes considers

1. Aonly conductor strand count✓
2. Bonly fuse element alloy only✓
3. Ctraffic volume, road type and pedestrian conflict areas✓
4. Donly synchronous condenser rating✓

Pole setback and overhang influence

1. Aonly neutral current in 4-wire system✓
2. Bonly rotor resistance of slip-ring motor✓
3. Conly Buchholz relay gas volume✓
4. Dlight distribution on carriageway and footpath✓

LED street lighting retrofit often improves

1. Aonly THD without any lumen gain✓
2. Bonly pole weight without optics✓
3. Cefficacy, life and controllability (dimming/scheduling)✓
4. Donly earth resistance of rod✓

Spacing between street lights is increased when

1. Aonly when lamps are removed✓
2. Bmounting height and luminaire candela distribution allow✓
3. Conly when voltage is reduced 50%✓
4. Donly when power factor is zero✓

Semi-cut-off and non-cut-off street lanterns differ in

1. Aamount of light allowed above horizontal (upward light)✓
2. Bonly lamp wattage without optics✓
3. Conly pole material wood vs steel✓
4. Donly supply neutral earthing✓

Average lux on road surface in street lighting design uses

1. Aonly Ohm law of conductor✓
2. Bonly Ferranti effect formula✓
3. Conly welding heat input equation✓
4. Dlumen method with utilization factor and maintenance factor✓

Mounting height of street lights affects

1. Aonly transformer tap position✓
2. Bonly cable insulation thickness only✓
3. Cspacing, uniformity and glare on the roadway✓
4. Donly motor synchronous speed✓

Cut-off luminaire in street lighting directs light

1. Aonly into the sky for astronomy✓
2. Bdownward to the road with limited upward spill✓
3. Conly into adjacent property without control✓
4. Donly horizontally at eye level✓

Lamp life rating (e.g., 1000 h incandescent, 50000 h LED) indicates

1. Aguaranteed illuminance lux level✓
2. Bmaximum supply voltage✓
3. Cearth loop impedance✓
4. Dstatistical median or rated hours to replacement criteria✓

Metal halide lamps are preferred for

1. Aonly indicator pilot lamps✓
2. Bgood color rendering and high efficacy in sports/factory lighting✓
3. Conly series street lighting without gear✓
4. Donly battery trickle charge✓

Starting voltage for fluorescent tube is highest at

1. Ahighest temperature always✓
2. Bzero humidity only condition✓
3. Clowest ambient temperature✓
4. Dfull lamp lumen output✓

Power factor of magnetic-ballast fluorescent luminaire is often improved by

1. Aremoving capacitor entirely always✓
2. Bhigh power factor or electronic ballast✓
3. Cusing only resistance ballast for unity PF✓
4. Dincreasing THD without correction✓

LED lamp efficacy compared to incandescent is generally

1. Aalways lower than 10 lm/W✓
2. Bequal to candle only✓
3. Cindependent of junction temperature✓
4. Dmuch higher (often 80–150+ lm/W)✓

Tungsten halogen cycle in halogen lamps

1. Aredeposits evaporated tungsten back on the filament✓
2. Beliminates all heat from filament✓
3. Creplaces need for glass envelope✓
4. Dconverts AC to DC✓

High intensity discharge (HID) lamps include

1. Amercury vapor, metal halide and high-pressure sodium✓
2. Bonly tungsten halogen without discharge✓
3. Conly neon sign electrodes without arc✓
4. Donly LED chip arrays✓

Compact fluorescent lamp (CFL) advantage over incandescent is

1. Alower efficacy than incandescent✓
2. Bno need for any phosphor✓
3. Chigher luminous efficacy and longer life✓
4. Doperation without any ballast ever✓

Fluorescent lamp requires ballast to

1. Aincrease filament resistance to infinity✓
2. Bconvert AC to DC at load only✓
3. Cmeasure earth fault current✓
4. Dlimit current and provide starting voltage✓

Incandescent lamp light is produced by

1. Agas discharge in mercury vapor only✓
2. Bheating a tungsten filament to incandescence✓
3. CLED junction electroluminescence✓
4. Dchemical combustion of fuel✓

Spacing to height ratio (SHR) in interior lighting relates to

1. Ashort-circuit level of substation✓
2. Buniformity of illuminance for a given luminaire distribution✓
3. Ctransformer impedance only✓
4. Dwelding electrode diameter only✓

Color rendering index (CRI) degradation in aging lamps

1. Amay be considered alongside lumen depreciation in critical areas✓
2. Bis unrelated to lighting maintenance✓
3. Creplaces illuminance calculation entirely✓
4. Deliminates glare completely✓

Emergency lighting levels are maintained considering

1. Aappropriate MF and minimum lux codes for escape routes✓
2. Bonly decorative color temperature✓
3. Conly highest HF ballast THD✓
4. Donly motor pull-out torque✓

Design illuminance with MF less than unity means installed initial lux is

1. Alower than maintained always✓
2. Bequal to zero always✓
3. Chigher than the target maintained illuminance✓
4. Dindependent of lamp choice✓

For LED luminaires, lumen maintenance is often quoted as

1. Aonly peak candela at 1 ms✓
2. BL70 or L80 life (hours to 70% or 80% initial lumens)✓
3. Conly THD of driver✓
4. Donly earth resistance✓

Cleaning luminaires on schedule improves

1. Aonly power factor of supply✓
2. Bonly cable insulation resistance✓
3. Conly short-circuit MVA✓
4. Deffective lumens reaching the work plane✓

Relamping before average lamp life in group relamping

1. Aalways wastes all lamps instantly✓
2. Beliminates need for MF✓
3. Cmaintains more uniform illuminance than spot relamping alone✓
4. Dreduces efficacy to zero✓

Combined maintenance factor MF is typically

1. Asum of LLD and DDF only✓
2. Balways equal to 2✓
3. Cproduct of LLD and DDF (and other factors if used)✓
4. Dindependent of cleaning schedule✓

Dirt depreciation factor (DDF) in lighting allows for

1. Aincreased lamp voltage only✓
2. Bmotor starting current✓
3. Ctransformer tap change✓
4. Dreduced light output due to dust on luminaires and room surfaces✓

Lamp lumen depreciation (LLD) factor represents

1. Aratio of voltage to current✓
2. Bpower factor of ballast only✓
3. Cratio of lumens at end of life to initial lumens✓
4. Dcable derating factor✓

Glare in lighting installations is reduced by

1. Ausing only bare lamps at low height✓
2. Bmaximizing direct glare toward eyes✓
3. Celiminating all diffusers always✓
4. Dproper shielding, mounting height and limiting luminance of sources✓

Utilization factor (UF) in interior lighting depends on

1. Aonly conductor resistivity✓
2. Bonly breaker making capacity✓
3. Conly grid frequency deviation✓
4. Droom geometry, reflectances and luminaire photometrics✓

Maintenance factor (MF) in lighting design accounts for

1. Aonly supply voltage rise✓
2. Blamp lumen depreciation and dirt depreciation over maintenance period✓
3. Conly transformer iron loss✓
4. Donly motor slip✓

Luminous flux required on a work plane depends on

1. Arequired illuminance and area (Φ = E × A)✓
2. Bonly lamp voltage✓
3. Conly power factor of motor✓
4. Donly cable length✓

A 100 W incandescent lamp producing 1700 lm has efficacy about

1. A17 lm/W✓
2. B100 lm/W✓
3. C1.7 lm/W✓
4. D170 lm/W✓

Luminous efficacy of a light source is

1. Awatts per lumen always below 1✓
2. Blumens produced per watt of input power✓
3. Ccandela per meter only✓
4. Dpower factor of lamp only✓

Luminous intensity of a point source is measured in

1. Acandela (cd)✓
2. Blux✓
3. Clumen per hour✓
4. Dohm✓

One lumen is defined in relation to

1. Aonly IR radiation power✓
2. Bradiant flux weighted by the luminous efficiency function V(λ)✓
3. Conly magnetic flux in weber✓
4. Donly cable charging VAR✓

Illuminance on a surface is measured in

1. Acandela only✓
2. Blumen✓
3. Cwatt per steradian✓
4. Dlux (lx)✓