1. Mirrors and Lenses
Physics
Spring 2002

2. Types of Mirrors Plane mirror- flat mirror
Ex. everyday, bathroom mirror
Convex mirrors - bend outward
Ex. the back of a spoon, sideview mirrors
Concave mirrors - bend inward
Ex. satellite dishes, the front of a spoon

3. Plane mirrors Image is behind the mirror - virtual image
Image is reversed back to front

4. Convex mirrors Image is behind the mirror - virtual image
Image is much smaller than object

5. Concave mirrors Principal Axis is from C to A
For small angles, the focal point is half the distance between the mirror and the Center, C. f F C A r

6. Spherical vs. Parabolic mirrors
Spherical mirrors do not focus everything at one point - spherical aberation.
Parabolic mirros DO focus everything at one point - used for flashlights, car headlights, etc.

7. Ray Diagrams
Incident light rays parallel to the principal axis are reflected through the focal point.
Incident rays through the focal point are reflected parallel to the principal axis. P1 P2 I1 I2

8. Mirror equation
The distance from the mirror to the object and the mirror to the image are related. = do di f do di

9. Mirror equation ctd. You can also find the magnification of an image.
Both m and hi are negative - image is inverted.
hi = -di = m ho do ho hi

10. Example
An object 2.0 cm high is 30.0 cm from a concave mirror. The radius of curvature is 20.0 cm. What is the location and size of the image? = do di f =
30 cm di
10 cm
= /cm
di = 15 cm

11. Example
An object 2.0 cm high is 30.0 cm from a concave mirror. The radius of curvature is 20.0 cm. What is the location and size of the image?
hi = -di = m ho do
hi = -di
x ho do
hi = 15 cm
x 2.0 cm
30 cm
= -1 cm