Ray Optics Test...

The distance between a point source of light and a screen which is 60 cm is increased to 180 cm. The intensity on the screen as compared with the original intensity will be

A source of light emits a continuous stream of light energy which falls on a given area. Luminous intensity is defined as

Venus looks brighter than other stars because

To prepare a print the time taken is 5 sec due to lamp of 60 watt at 0.25 m distance. If the distance is increased to 40 cm then what is the time taken to prepare the similar print

A lamp is hanging lm above the centre of a circular table of diameter lm. The ratio of illuminaces at the centre and the edge is

A lamp is hanging at a height of 4m above a table. The lamp is lowered by lm. The percentage increase in illuminace will be

The intensity of direct sunlight on a surface normal to the rays is I₀. What is the intensity of direct sunlight on a surface, whose normal makes an angle of 60° with the rays of the sun

Inverse square law for illuminance is valid for

1% of light of a source with luminous intensity 50 candela is incident on a circular surface of radius 10 cm. The average illuminance of surface is

Two light sources with equal luminous intensity are lying at a distance of 1.2 m from each other. Where should a screen be placed between them such that illuminance on one of its faces is four times that on another face