The illuminance on a surface is 3.5 lux, and the surface is 2 meters from the light source. what’s the intensity of the source?

The intensity is 49 Candelabra

The formula for calculation the luminous intensity is;

Luminous intensity = illuminance × square radius

Lv = Ev × r²

 = 3.5 × 2²

= 3.5 × 14

 = 49 Candelabra

the duration of a photographic flash is related to an rc time constant, which is 0.100 μs for a certain camera.

i believe the answer is a hope it and is correct