1. Lenses

2. Lenses by pieces

3. Converging Lens
Focal Length
Lens axis
Principal focus

4. Converging Lenses

5. Diverging Lens F

6. Diverging Lenses

7. Equations – the SAME!

8. Sign conventions

9. Example 23.6
A converging lens has a focal length of 12 cm. For an object at (a) 60 cm, (b) 15cm, and (c) 8.0cm from the lens, where is the image formed, and what are its characteristics?

10. Example 23.8
An object is 24 cm in front of a diverging lens that has a focal length of -15cm. (b) Find the location and characteristics of the image with the thin lens equations.

11. Nearsightedness
Nearsightedness is usually caused by the converging lens in the eye being too strong, which means it brings the rays together in front of the retina, so that the image on the retina is not focused properly, and is blurred.
Diverging lenses are used in glasses that correct short sight. 

12. Farsightedness
Farsightedness is where people cannot make the lens fat enough to see close-up objects clearly.
The converging lens brings the rays in so that the image is focused correctly on the retina.

13. What kind of lens?

14. Nearsighted or Farsighted?

15. Microscope eyepiece objective lens final virtual image object
real image fo fe fo fe

16. Telescope