A surface is illuminated by a light source. If the angle between the normal at a point on the surface and the direction of luminous flux changes from 30° to 60°, what is the ratio of change in the illumination?
1
\( \sqrt 3 :1\)
2
2 ∶ 1
3
4 ∶ 1
4
\( \sqrt 2 :1\)