1. Lenses
Mirrors reflect.
Lenses refract.

2. Convex Lens (converging)

7. Pull out the iris – it should be between the cornea and the lens, but may have stayed with the back of the eye
The hole in the centre of the iris is the pupil, which lets light into the eye
Remove the lens
It is a clear lump about the size and shape of a squashed marble

8. The lens feels soft on the outside and hard in the middle
Hold the lens up and look through it – what do you see?
Put the lens down on a newspaper and look through it at the words – what do you see?

12. Concave Lens (diverging)

15. Normal Eye

16. Myopia (Short sightedness)

19. Mirrors Lenses Light is reflected Concave mirror ‘converges’
Convex mirror ‘diverges’
Lenses
Light is refracted
Concave lens ‘diverges’
Convex lens ‘converges’

20. Ray
Diagrams

21. Drawing Ray diagrams – Lenses
Draw two rays from the top of the object – “parallel to focus” then “focus to parallel”
Find the point where the two refracted rays intersect – if they don’t, go backwards and draw dotted lines (the image is then virtual)

22. Convex Lens – Case 1

26. Convex Lens – Case 2

27. Convex Lens – Case 3

28. Convex Lens – Case 4

29. Convex Lens – Case 5

30. Convex (Converging) Lens
Size
Orientation
Nature
Behind 2F
At 2F
Between 2F & F
At F
Between F & P

31. 1. 2. 3. 4. 5.

32. Convex (Converging) Lens
Size
Orientation
Nature
Behind 2F
Diminished
Inverted
Real
At 2F
Same
Between 2F & F
Enlarged
At F
No image
Between F & P
Upright
Virtual

33. Concave Lens

37. Convex (converging) lenses
The image will be real and inverted if the object is located further away than the focal length.
The image will be virtual, upright and enlarged if the object is located between the lens and the focal point.
Concave (diverging) lenses
Concave lenses always produce virtual images which are always upright and smaller than the objects.