CH 32: geometric optics

Reflection:Reflection is the simplest method for changing the direction of light.

Reflection – Light incident on a boundary between two mediums is absorbed and reemitted back into the original medium.

Incident Ray Reflected Ray

Surface Normal

qi qr

When light is reflected from a surface it takes the path of least time.

This will correspond to the path of least distance since the speed is constant.The path of least distance requires that the angle of incident be equal to the angle of reflection.

i r Law of Reflection

qi – incident angleqr – reflected angle

The angle is always measured relative to the surface normal!!

The law of reflection holds true for all electromagnetic waves. There are two main categories of reflection.Specular reflection – light reflected off of a smooth surface. Reflected rays will all be parallel.

Diffuse reflection – light reflected off of a rough surface. The reflected rays are in a variety of directions

Smooth surface – irregularities are smaller than the wavelength of the light.

An observer O, facing a mirror, observes a light source S. Where does O perceive the mirror image of S to be located?

1. 12. 23. 34. 45. Some other location.6. The image of S cannot be seen by O when O and S are located as shown.

Gwen seems a bit perplexed as she views her image in the plane (flat) mirror.

She is perplexed because she cannot figure out exactly how to describe her image in the mirror.When you view your image in a plane mirror, is your image (1) inverted top-to-bottom? (2) inverted left-to-right? (3) inverted front-to-back? (4) not inverted at all? You may vote for as many of the above answers as you wish, as long as you are consistent.