Q. A lamp of 250 candela power is hanging at a distance of 6 m from a wall. The illuminance at a point on the wall at a minimum distance from lamp will be
A) 9.64 lux
B) 4.69 lux
C) 6.94 lux
D) None of these
Explanation
(c) At minimum distance, incidence is normal. Therefore, $E = \frac{I}{r^{2}} = \frac{250}{6^{2}} = 6.94\ $lux
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.