A spherical light bulb with a diameter of `3.0cm` radiates equally in all the directions with a power of `4.5piW.`(a find the light intensity of the surface of the bulb.(b) Find the light set up with its axis pointing towards the bulb.The lens has a circular face with a diameter of `15.0cm`and a focal length of `30.0cm`Find the diameter of the image of the bulb formed on a screen kept at the location of the image .(d)Find the light intensity at the image.

Answer

(a) `5000 W//m^(2)`; (b) `0.02 W//m^(2)` (c) `0.125 W//m^(2)` (d) `288 W//m^(2)`