To print a photograph from a negative, the time of exposure to light from a lamp placed 0.50m away is 2.5s. How much exposure time is required if the lamp is placed 1.0w away ?

A satisfactory photographic print is obtained when the exposure time is 10 sec at a distance of 2m from a 60 cd lamp. The time of exposure required for the same quality print at a distance of 4m from a 120 cd lamp is

The proper exposure time for a photographic print is 20 s at a distance of 0.6 m from a 40 candle power lamp. How long will you expose the same print at a distance of 1.2 m from a 20 candle power lamp ?

A good photographic print is obtained by an exposure of two seconds at a distance of 20 cm from the lamp. Calculate the time of exposure required to get an equally good result at a distance of 40 cm.

when a monochromatic point source of light is at a distance 0.2 m from a photoelectric cell, the saturation current and cut-off voltage are 12.0 mA and 0.5 V. If the same source is placed 0.4 m away from the photoelectric cell, then the saturation current and the stopping potential respectively are

A lamp placed 70.0 cm from a screen on one side produces the same illumination as a standard 60 cd lamp placed 105 cm away on the other side of the screen. What is the luminous intensity of the first lamp ?