Which of the following statement is correct?

ψ Wave length for red colour is

From a uniform light source of 300 c.p. there exists a plane surface 15 m below the value of illumination on the plane surface when the luminous flux rays are inclined at an angle of 30 to the surface is

The unit of solid angle is

Total flux or lumens required in any lighting scheme depends inversely on

Solid angle is expressed in terms of

A 200 candle power lamp is hung 4 m above the centre of circular area of 5 m diameter. The illumination at centre of the area is

___________________________ factor is defined as the ratio of the illumination when everything is clean to illumination under normal working conditions.

Candela is the unit of which?

Candela is the unit of

In illumination technology total lumens emitted by source / total lumens available after waste of light is equal to

What will be the total flux emitted by a source of 60 candle power?

A solid angle can be expressed in terms of

Illumination can be expressed in

Unit of luminous flux is

Carbon arc lamps are commonly used in

Radiant efficiency of the luminous source depends on

The illumination of the surface varies directly with cosine of the angle between normal to surface and direction of the inclined light is given by

Luminous efficiency of a fluorescence lamp is

The solid angle subtended by an area of 2400 cm² on the surface of a sphere of diameter 1.2 m is