Question

$1$ % of light of a source with luminous intensity $50$candela is incident on a circular surface of radius $10cm$. The average illuminance of the surface is

• A. $100$ lux
• B. $200$ lux
• C. $300$ lux
• D. $400$ lux

Answer 1

The correct option is B $200$ lux

Illuminance = $\frac{Luminousintensity\times 4\pi }{area}$

=$\frac{50\times 4\pi }{100\times \pi \times 0.1\times 0.1}=200lux$

Answer B) $200lux$