Question

A point source emitting 628 lumen of luminous flux uniformly in all directions is placed at the origin. Calculate the illuminance on a small area placed at (1.0 m, 0, 0) in such a way that the normal to the area makes an angle of 37° with the X-axis.

Answer 1

I = luminous intensity =628/4π
= 50 Candela
r = 1m, θ= 37°
So, illuminance, E =Icosθ/r²
= 50x cos37º/1²
= 40 flux