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 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?

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 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.

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 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?

An unshaded lamp is placed at a distance \(r_1\) above the ground and produces an illumination \(E_1\) at a point on the ground directly below the lamp. At what angle must the lamp be aimed on the ground to produce an illumination one-half of \(E_1\)?

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.

An office 17m by 8m wide, is lighted by 8 lamps has a luminous intensity of 200 Cd. Allowing an absorption loss of 4,000 lm for the reflectors, walls and ceiling, Calculate the average illuminations on the working plane.

An office 15 m by 8 m is lighted by 8 lamps, each with a luminous intensity of 200 cd. Allowing an absorption loss of 4,000 lm for the reflectors, walls and ceiling, calculate the average illumination on the working plane.

A road is illuminated by two 500 candela lamps placed 6.1 m above the center line of the road and 18.3 m apart. Find the illumination produced on the surface of the road at a point on the center line midway between the lamps.

An office, 17m by 8m, is lighted by 10 lamps and each lamp has a luminous intensity of 200 cd. Allowing an absorption loss of 5,000 lm for the reflectors, walls, and ceilings, calculate the average illumination on the working plane.

A colliery workshop 20 m x 10 m requires an average illumination of 135 lm/m² on the working plane. Calculate the electrical power and current required for the purpose. Allow a coefficient of utilization of 0.45 and a depreciation factor of 1.4. The supply is 230-V at 50 Hz and the efficiency of each of the lamps is 12 lm/W.