1. 5.3: Using Lenses to Form Images

3. Lenses
A lens is a curved piece of transparent material that refracts light.
Light rays passed through a lens are either converged or diverged.
2 types of lenses:
1) Concave Lenses
2) Convex Lenses

4. Concave Lenses
Concave lenses are thinner in the middle (thicker on the edges).
As rays of light shine through a concave lens, the rays diverge.
Uses: used in some types of eyeglasses & some telescopes

8. Images Made by Concave Lenses
Concave lenses are used to produce images that are smaller and upright compared to the real object.

10. Convex Lenses
Convex lenses are thicker in the middle (thinner on the edges).
Parallel light rays passing through a convex lens converge and meet at a focal point.
Rays that strike the more curved surface of the lens bend more…

14. Images Made by Convex Lenses
Images can be produced using convex lenses.
For example, convex lenses are used in magnifying glasses, in overhead projectors and in cameras.
An image can be projected onto a screen using a light and a convex lens!

15. Focal Length
Focal length is just the distance from the center of the lens to the focal point.

16. Depends on Focal Length
How Images Appear
Depends on Focal Length
The image size and orientation depends how many ‘focal lengths’ away the object is from the lens.

17. Focal Length and Image Distance from Lens Image
- More than 2 focal lengths = smaller, upside down

19. Distance from Lens Image
- More than 2 focal lengths = smaller, upside down
B/w 1 and 2 focal lengths = larger, upside down

20. Less than 1 focal length= larger, right side up
Distance from Lens Image
- More than 2 focal lengths = smaller, upside down
B/w 1 and 2 focal lengths = larger, upside down
Less than 1 focal length= larger, right side up

21. Less than 1 focal length= larger, right side up
Distance from Lens Image
- More than 2 focal lengths = smaller, upside down
B/w 1 and 2 focal lengths = larger, upside down
Less than 1 focal length= larger, right side up
At focal point = no image