1. Physics
Section 13-2
Plane mirror optics

2. Section 13-2 Plane mirror optics
Mirrors were originally highly polished metal surfaces, such as these Egyptian mirrors. Metal coated glass mirrors actually date back as far as the first century A.D., and Pliny mentions mirrors using gold leaf reflective surfaces in 77 A.D.
Glass coated with a tin-mercury amalgam was perfected in medieval Europe. The first silvered mirrors were invented by Justus von Liebig in 1835.

3. Galerie des Glaces (1690), Château de Versailles
The mirrors in this famous French royal hall at Versailles show signs of metal corrosion due to age.

4. Law of reflection θr = θi
The law of reflection for mirrors is the same for any wave reflection. The angle of reflection to a line normal to the point of reflection is equal to the angle of incidence.
θr = θi
normal line

5. Smooth and rough surfaces
Mirrored surfaces, such an aluminized glass surface or a still mountain lake, are very smooth. All incident rays will be reflected at the same angle. This creates a perfect mirror image of any object. This is specular reflection. On the other hand, rougher surfaces, such as a white wall, reflect light in many direction. This is diffuse reflection.
Diffuse reflection still obeys the law of reflection.

6. Specular and diffuse reflection are very important in art and computer graphics modeling.

7. Images in plane mirrors
Light rays incident from a point will diverge after reflection. To the eye, the rays appear to originate from a point behind the mirror. No real light actually passes through this point. The image produced is a virtual image.
object
point
image
point

8. ho hi do di
real space
virtual space + –
hi = ho
di = –do

9. Plane mirrors cause lateral inversion (“mirror images”).