1. Chapter 18
Mirrors/lenses

2. Concave mirrors

3. Uses?

4. Convex mirrors

5. Uses?

6. Formulas and problems
Lens/Mirror equation 1/f = 1/di + 1/do Magnification Focal length m = hi/ho f = r/2 m = -di/do Image height hi = -ho (di/do)

7. A 4 cm high candle is placed 10 cm from a concave mirror having a focal length of 16 cm. Find the location and height of the image.

8. A 4 cm high candle is placed 10 cm from a concave mirror having a focal length of 16 cm. Find the location and height of the image. What we know: ho = 4 cm di = ? do = 10 cm hi = ? f = 16 cm

9. Solving for di
Use the lens/mirror equation to find di when possible
1/16 = 1/di + 1/10
1/16 - 1/10 = 1/di
1/di =
di = 1/-.0375
di = cm
So, the image is 26.6 cm away from the mirror, and it is inverted (that’s what the negative sign means)

10. Solving for hi
Use hi = -ho (di/do) hi = -4 (-26.6/10) hi = cm

11. Work: Page 425 #’s 2-3 (do not draw ray diagrams, just solve)