Using the law of reflection, explain how powder takes the shine off of a person’s nose. what is the name of the optical effect?

1 Answer
Jul 30, 2014

The powder makes the surface uneven which disperses the light.

The angle of reflection is equal to the angle of incidence. The angles are measured from the normal line, which is normal (perpendicular) to the surface.

The rays of light reflected from the same region on a smooth surface will be reflected at similar angles and so all be observed together (as a "shine").

When powder is put on a smooth surface it makes the surface uneven. So the normal lines for incident rays in a region on the surface will be at different orientations. Now the rays reflected from the same region will be reflected at different angles so the observer will only observe some rays together – hence no "shine".

Light reflection and angles with powder