Illumination

The meter movement in an illumination meter directly measures

A direct lighting fixture directs at least

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

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.

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.

The ratio of lumens reaching the work plane divided by the total lumens generated by the light is:

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?

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 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?

The study of illumination involves

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.

Two lamps having luminous intensities of 250 and 300 candelas respectively are placed 100 m apart. Lamp A is 10 m above the ground while lamp B is 20 m above the same level. What is the illumination at ground level midway between the lamp posts?

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.

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

The luminous intensity is defined as

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.