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 convex lens of power 4D is placed at a distance of 40 cm from a wall at what distance from the lens should a candle be placed so that its image is formed on the wall?

An intensity of illumination of 4 flux is required at a distance of 5m from an electric lamp. What must be the luminous intensity of the lamp?

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.

A convex lens of power 4 D is placed at a distance of 40 cm from a wall . At what distance from the lens should a candle be placed so that its image is formed on the wall ?

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 ?

A lamp is placed at a distance of 16 cm, from a photocell and the current observed is 1 mA. If the distance from the lamp is reduced to 8 cm, the photocurrent now will be

A lamp is placed at a distance of 16 cm, from a photocell and the current observed is 1 mA.If the distance from the lamp is reduced to 8 cm, the photo current now will be

A 16 cd lamp placed at a distance of 125 cm from a screen produces the same illuminance on the screen as that produced by a bulb placed at a distance of 175 cm from the scree. If the bulb takes 0.85 A current at 110, find its efficiency.

A lamp is placed at a distance of 8 cm from a photocell and the microammeter records a current of 100 mu A . If the lamp is kept at a distance of 4 cm from the photocell, the photoelectric current recorded by the microammeter will be

A 2.5 cm high candle flame is placed at a distance of 2.5 m from a wall. How far from the wall a concave mirror must be placed so that a 7.5 cm high inverted image of the flame is formed on the same wall? Also calculate the focal length of the mirror.