The candle power of a lamp placed normal to a working plane is 60 CP. Find the distance if the illumination is 15 lux?

• A. 2.5 meters
• B. 2 meters
• C. 4 meters
• D. 1.5 meters

Answer: (B)

Candle Power of lamp = 60 CP
Illumination of lamp = 15 lux
Distance(D) = ? meters
Illumination of lamp = (candle power)/(distance)2
(D)2 = candle power/Illumination of lamp
(D)2 = 60/15 =4
D = √4
D = 2