Illumination

An unshaded lamp is 6 m above a table. It is lowered down by 2 m. By how much is the illumination on the table increased?

A medium unshaded lamp hangs 8 m directly above the table. To what distance should it be lowered to increase the illumination to 4.45 times its former value?

A floodlight emitting 25,000 candelas in the center of its beam is aimed at 60° to a point on the ground 20 meters away. The illumination of the point in lux is

An unknown lamp placed 6 m from a photometer screen provides the same illumination as a 90-cd lamp placed 4 m from the screen. What is the candlepower of the unknown lamp?

Luminaires of 2000 lumens output will be installed in a room. The desired illumination is 200 foot-candle. The coefficient of utilization is 0.45 and maintenance factor is 90%. Determine the number of luminaires needed if the size of the room is 120 m².

A hall 30 m long and 12 m wide is to be illuminated and the illumination required is 50 meter-candles. Calculate the number of lamps required taking a depreciation factor of 1.3 and utilization coefficient of 0.5 given that the output of the lamp to be used is rated 100 W, 1615 lumens.

The floor area of a room is 10 meters by 10 meters. The desired illumination level is 150 lux. Assume the coefficient of utilization is 0.51, the maintenance factor is 0.95 and in the market a fluorescent luminaire provide 1200 lumens output of light. Determine the number of luminaires needed for the room.

A lamp produces an illumination of 10 lux at a point 10 m directly below it. What is its luminous intensity?

A standard candle emits a total luminous flux of _ lumens.

An unshaded lamp is 6 m above the table. It is lowered down by 2 m. By how much is the illumination on the table increased?

Calculate the distance from a normally placed screen a 30 candela lamp be placed in order that the illumination be 5 lux.

A medium unshaded lamp hangs 8 m directly above the table. To what distance should it be lowered to increase the illumination to 2 times its former value?

Calculate the mean spherical candle power of a lamp emitting a flux of 1,500 lumens.

A lamp produces an initial illumination of 800 lux over a normally placed screen. If the distance of the lamp from the screen is doubled, what is the new illumination on the screen?

A lamp produces an illumination of 10 lux at point 10 m directly below it. What is luminous intensity of the lamp?

A room 8 m × 12 m is lighted by 15 lamps to a fairly uniform illumination of 100 lumens per square meter. What is the coefficient of utilization if the output of each lamp is 1,600 lumens?

A lamp has a luminous efficiency of 11 lm/watt and gives out a luminous flux of 275 lm. What is the wattage of the lamp?

A uniform source of light gives 1,884 lumens and is suspended 4 m above the center of a floor 3 m square. Find the illumination in lm/m² at the floor level directly below the lamp.

A 100 watt, 230 volt gas filled lamp has a mean spherical candlepower of 92. Find its efficiency in lumens per watt.

A 100 watt, 230 volt gas filled lamp has a mean spherical candle power of 92. Find its efficiency in lumens per watt.