Mathematics

Problem

A wall behaves as an ideal diffuse (Lambertian) reflector, so the reflected intensity

I

varies with viewing angle

\theta

from the surface normal according to

I \propto \cos\theta

. A sensor measures an intensity

I_{30}

when it is placed

30^\circ

from the normal. What intensity, expressed as a multiple of

I_{30}

, will the same sensor measure if it is moved to

60^\circ

from the normal? a)

0.50\,I_{30}

0.58\,I_{30}

0.67\,I_{30}

0.33\,I_{30}