A light is to be placed on a wall in order to obtain maximum brightness of illumination. To achieve this brightness, how high on the wall should this light bulb be placed to a point on the floor that is 3.6 m from the wall?
A2.54 m
B2.25 m
C2.08 m
D2.86 m
#2📘 1001 RojasHard
Two lamps x and y are hanged at a distance of 20 feet between their centers and 10 feet above the working surface. Lamp x gives 140 cp while lamp y gives 230 cp. At what distance from a point directly below lamp x on the line joining their centers will the two lamps give equal amount of illumination?
A8.22 ft
B8.34 ft
C8.05 ft
D8.72 ft
#3📜 EE Pre-Board August 2017📘 PowerhouseHard
Two lamps having luminous intensities of 250 and 300 candelas respectively are placed 100 m apart. Lamp A is 10 m above the ground while lamp B is 20 m above the same level. What is the illumination at ground level midway between the lamp posts?
