Two 16 candela lamps are placed on the same side of a secreen at distance of 2 m and 5 m form it. Caluclate the distance at which a single 32 candela lamp must be placed in order to give the same intensity of illumination.

A book placed at a distance of 30 cm from a candle can be read. What is the maximum distance at which a lamp of 32 candela can be still possible to read The book ?

Two light sources of intensities 8 cd and 12 cd are placed on the same side of a photometer screen at a distance of 40 cm from it. Where should a 80 cd source be placed to balance the illuminance ?

A lamp of 120 candela hangs at a height of 4 m excathy above the centre of a circular table of diameter of 6.m Caluclate the illuminance at the centre and at the edge of the table.

A lamp of luminous intensity 50 candela is placed at a distancde of 1 m from a wall What is the illuminacnce of the wall directly in front of lamp ? If another lamp of 100 cd is placed on the same line at a distance of 125 cm what is the illuminance now?

A candle flame 2 cm high is placed at distance of 2 meter from a wall. How far from the wall must a concave mirror to placed in order to form an image of the flame 6 cm high on the wall ?

A photographic print is found satisfactory when the exposure was for 16 s at a distance of 20 m from a 25-watts lamp. At what distance must the same paper be held from a 50-watts lamp in order that an exposure of 25 a may give the same result?

What distance should be two plates each of area 0.2xx0.1 m^(2) of an air capacitor be placed in order to have the same capacitance as a spherical conductor of radius 0.5 m?

Two lamps balance on the shadow photometer at distance of 0.60 m and 0.42 m from the screen. The stronger is then covered with a glass shade whicht transmits 80% of the incident light. How far must be the other lamp be displaced in order to restore balance?

A lamp of luminous intensity 100 cd is held at a distance of 2 m from a vertical wall. A plane mirror is fixexd on the opposite wall which is at a distance of 4 m from the lamp. Calculate the illumainance on the wall opposite to the mirror at a point on the horizontal line through the lamp. Also calculate the luminous flux on a small area or 0.02 m^(2) surrounding the point.