The luminous flux of a 1 W sodium vapour lamp is more than that of a 10 kW source of ultraviolet radiation. Comment.

Calculate the number of photons emitted per second by a 10 W sodium vapour lamp. Assume that 60% of the consumed energy is converted into light. Wavelengths of sodium light =590nm.

Find the luminous flux of 10 W source of 600 nm. The relative luminosity at 600 nm is 0.6.

The luminous flux of a monochromatic source of 1 W is 450 lumen W^-1 . Find the relative luminosity at the wavelength emitted.

A circular area of radius 1.0 cm is placed at a distance of 2.0 m from a point source. The source emits light uniformly in al directions. The line joining the source to the center of the area is normal to the area. It is found that 2.0xx1^-3 lumen of luminous flux is incident on the area. Calculate the total luminous flux emitted by the source and the luminous intensity of the source along the axis of the area.

The overall luminous efficient of a 100 W electric lamp is 25 lumen W^-1 . Assume that light is emitted by the lamp only in the forward half, and is uniformly distributed in al diredctionsin this half. Calculate the luminous flux falling on a plane object of area 1cm^2 placed at a distance of 50 cm from the lamp and perpendicular to the line joining the lamp and the object.

About 5% of the power of a 100 W light bulb is converted to visible radiation. What is the average intensity of visible radiation a. at a distance of 1m from the bulb b. at a distance of 10m Assume that the radiation is emitted isotropically and neglect reflection.

A country has a food deficit of 10%. Its population ear. Its annual food production every year is 4% more than that of the last year Assuming that the average food requirement per person remains constant, prove that the country will become self-sufficient in food after n years, where n is the smallest integer bigger than or equal to (log_e 10-log_e 9)/((log_e 1.04)-0.03)

A photographic plate records sufficient intense lines when it is exposed for 12 s to a source of 10 W. How long should it be exposed to a 12 W source radiating the light of same colour to get equally intense lines ?