Illumination

A piece of paper lies on a table 2 m away from a point directly below a bulb of 100 cd and is 4 m. above the table. Calculate the illumination on the center of the paper in lux.

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?

An unshaded lamp is placed 95 cm from the screen of a photometer. If a glass is placed between the screen and the lamp, the lamp must be moved 5 cm closer to the screen to produce the same illumination as before. The glass blocks what percent of the light produced by the lamp?

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?

Two lamps A and B having intensities of 300 cp and 500 cp respectively are situated 12 ft apart. A screen is placed between them in order that the illuminations on any sides are equal. How much is this illumination?

A light is to be placed on a wall in order to obtain maximum brightness of illumination. To achieve this brightness, how high on the wall should this light bulb be placed to a point on the floor that is 3.6 m from the wall?

Two lamps x and y are hanged at a distance of 20 feet between their centers and 10 feet above the working surface. Lamp x gives 140 cp while lamp y gives 230 cp. At what distance from a point directly below lamp x on the line joining their centers will the two lamps give equal amount of illumination?

A 100-cd lamp, which emits light uniformly in all directions, is suspended 2.5 m above the center of the working table, which is 3 m square. Calculate the illumination at each corner of the table.

A lamp of 500 cd is placed at the center of a room, 20 m x 10 m x 5 m. Calculate the illumination in each corner of the floor.

Four lamps are suspended 6 m above the ground at the corners of a lawn 4 m on each side. If each lamp emits 250 cd, calculate the illumination at the center of the lawn.

A lamp of 500 cd power is placed at the center of a room, 20 m x 10 m x 5 m. Calculate the illumination in a point in the middle of a 10 m wall at a height of 2 m from the floor.

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 35 m x 20 m is to be provided with a general illumination of 130 lux. If the depreciation factor is 1.4 and the coefficient of utilization is 0.50, determine the number of fluorescent lamp required. Assume luminous efficiency of the fluorescent tube as 50 lumens per watt for 80-watt lamp.

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.

A room 20m x 10m is to be illuminated by eight lamps and the average illumination is to be 50 lumens per square meter. If the utilization factor is 0.48 and depreciation factor 1.2, calculate the mean spherical power per lamp.

It is required to provide an illumination of 150 meter-candle in a factory hall 45 m x 15 m. Assume that the depreciation factor is 0.80, coefficient of utilization is 0.40 and efficiency of the lamp is 20 lumens per watt. Calculate the number of 250 W lamps.

The illumination of a room is being designed. The data as follows:
Room length = 30 ft
Room width = 20 ft
Coefficient of utilization = 0.6
Maintenance factor = 70%
Required foot-candle = 50
Lumens per lamp = 3300
Watts per lamp = 53
Voltage = 220
Power factor = 75%
What is the total current of the lamp required to satisfy the requirement?

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.