1. SEEING THROUGH A LENS

2.  We see the world through lenses.  Eye glasses = lenses. Contact lenses = lenses.  Magnifying glasses = lenses. Microscopes = lenses. Camera = lenses.

3.  What about individuals that do not need visual aids? Yes, they still see the world through lenses in their eyes. A lens!!

4. 2 TYPES  Convex (Converging) Lens  Parallel light rays converge (come to a single point) after refraction through the lens.  Concave (Diverging) Lens  Parallel light rays diverge (move away from each other) after refraction from the lens.

5. CONVEX LENS  F = Primary Focus (2 x F = 2F)  O = Optical Centre  F’ = Secondary Focus (2 x F’ = 2F’); located on same side as incident rays

6. CONVEX CHARACTERISTIC RAYS  Any incident ray passing through the Secondary Focus will…  REFRACT PARALLEL TO THE PRINCIPAL AXIS

7. CONVEX CHARACTERISTIC RAYS  Any incident ray passing through the Optical Centre will…  PASS UNDEVIATED (STRAIGHT THROUGH)

8. CONVEX CHARACTERISTIC RAYS  An incident ray parallel to the principal axis will…  REFRACT THROUGH THE PRIMARY FOCUS

9. CONVEX CHARACTERISTIC RAYS  Any incident ray passing through 2F’ will…  REFRACT THROUGH 2F

10. NOTE  These rules only apply to THIN lenses  Refraction (Lateral displacement) would occur otherwise.

11. ANOTHER VIEW

12. PREDICTING IMAGES IN A CONVEX LENS  Object located beyond 2F’  Where is the image?  The object appears to come where the light originates from.  The image is also located where all the rays come together.

13. LOST (LAST)  Location: Between F & 2F  Attitude/Orientation: Inverted  Size: Smaller than object  Type: Real (Different from Mirrors)

14. CONCAVE CHARACTERISTIC RAYS  Any incident ray parallel to the principal axis will…  REFRACT AS IF IT HAD PASSED THROUGH THE PRINCIPAL FOCUS

15. CONCAVE CHARACTERISTIC RAYS  Any incident ray moving toward the Secondary Focus will…  REFRACT PARALLEL TO THE PRINCIPAL AXIS

16. CONCAVE CHARACTERISTIC RAYS  Any incident ray passing through the Optical Centre will…  PASS UNDEVIATED (GO STRAIGHT THROUGH)

17. PREDICTING IMAGES IN A CONCAVE LENS  Object located beyond 2F  Where is the image? All the refracted rays diverge!  If the rays diverge, the image is where the refracted rays appear to meet in the opposite direction!

18. LOST (LAST)  Location: Same side as object  Attitude (Orientation): Upright  Size: Smaller than object  Type: Virtual (Different from Mirrors)