Question

In the above problem, the luminance of blotting paper is

• A. $3$ phot
• B. $3$ lux
• C. $4$ phot
• D. $4$ lux

Answer 1

The correct option is B $3$ lux

The source of luminance of the blotting paper is the light reflected by it. Since 75 % of light is reflected,

luminance = $\frac{100}{5^2}\times \frac{75}{100}$ = 3 lux

Answer. B) 3 lux