The light from a torch is normally incident on the surface at intensity of illumination I1. If the surface is tilted to 45∘ from initial position, then what will be intensity of illumination I2 on the surface in terms of I1 ?
The correct option is AI2=I1√2
Intensity I=PA where P is the power of incident light and A is the area of surface.
Then, I1=PA and I2=PA′ From the diagram, A′cos45∘=A ⇒I2=PAcos45∘=I1√2