2. 29.1 - Reflection Light incident upon a boundary between
two medium causes a portion of the light
to return back to original medium – reflection
All wave energy returned – totally reflected
Some energy reflected some transmitted – partially reflected
Metals are almost totally reflective – why so shiny
Water and glass reflect a much smaller amount (2% & 4%)

3. 29.2 – The Law of Reflection
Light rays reflect at the same angle as they are incident
Angle of incidence = angle of reflection
These angles are measured to the perpendicular of the surface – called the normal

4. 29.3 - Mirrors An infinite number of light rays leave the candle
Each obeys the law of reflection
Only some reflect back to your eye
These appear to come from behind the mirror
There is no light behind the mirror – a virtual image is produced
Flat mirrors only produce virtual images

5. Your eye cannot tell the difference between real and virtual images
Light enters the eye the same way
For flat (plane) mirrors, the image appears the same distance behind mirror as object is in front
The image and object are the same size

6. 29.4 – Diffuse Reflection
If a surface has imperfections about the size of one wavelength or larger – light “sees” it as rough
The reflections produced are in many different directions, that is, diffuse reflection
If wavelength larger than imperfections, the surface is considered smooth (specular reflection)
Therefore, reflections can only be seen at particular angles – equal to angle of incidence

7. 9.4 ½ - Curved Mirrors Shaped like sections of a sphere
May be reflective on inside (concave - converging) or outside (convex - diverging)

8. 29.4 ½ - Curved Mirrors
Parallel rays incident on a concave mirror reflect at common point called focal point (F)
The distance between focal point and mirrored surface – focal length (f)
The center of sphere that produced mirror curve, center of curvature, C = 2 f

9. To generate a ray diagram – three rays are used, all begin on the object
A parallel ray is reflected through focal point
A ray through the focal point is reflected parallel
A ray perpendicular to mirror reflects back on itself (goes through the center of curvature)

10. 29.4 ½ - CONT. There are three descriptors for the image produced
Real or virtual (or none)
Upright or inverted
Larger or smaller (or same size)

11. 29.4 ½ - CONCAVE - CONVERGING
Object outside the center of curvature (2 f) – image is real, inverted & smaller

12. 29.4 ½ - CONCAVE - CONVERGING
Object inside focal point – image is virtual, upright and larger

13. 29.4 ½ - CONVEX - DIVERGENT
For convex mirrors, the rays diverge after reflecting off mirror
Since they never meet in “front” of mirror, they never form real images
We backtrace imaginary rays behind mirror

14. 29.4 ½ - CONVEX - DIVERGENT
For a convex mirror – image is always virtual, upright & smaller

15. 29.4 ½ - MIRROR SIGN CONVENTION
CONCAVE
f is positive
Image can be real or virtual
Real image is always inverted can be larger or smaller
Virtual image is always upright and larger
CONVEX
f is negative
Image is always virtual
Image is always upright and smaller