A lamp giving out 1200 lm uniformly in all directions is suspended 8 m above the working plane. Calculate the illumination at a point on the working plane 6 m away from the foot of the lamp.

Find the total luminous output (lumen) of a filament lamp if the wattage of the lamp is 550 W and its luminous efficiency is given as 2 candle power per Watt.

A hall of size 25 m by 25 m is to be illuminated with 60 lux. If the lamp efficiency is 50 lumens/watt, the utilization factor is 0.8, and the candle power depreciation factor is 0.25, the total wattage required is: