Uses of lenses

1. Uses of LensesUses of Lenses
November 7, 2012November 7, 2012

2. ObjectivesObjectives
1.1.Diagram the different types of lensesDiagram the different types of lenses
2.2.Describe the different uses of lensesDescribe the different uses of lenses
3.3.Explain how lenses functionExplain how lenses function

3. Types of LensesTypes of Lenses
concave lens – where light that passes concave lens – where light that passes
through diverges as if it came from a pointthrough diverges as if it came from a point

4. Convex lens – where light that passes Convex lens – where light that passes
through converges to a single pointthrough converges to a single point

6. What are Lenses Used for?What are Lenses Used for?
1.1.Camera’sCamera’s
2.2.TelescopesTelescopes
3.3.Eyeglasses/ContactsEyeglasses/Contacts

7. Camera’sCamera’s
Pinhole Camera:Pinhole Camera:
–Simplest of camera’sSimplest of camera’s
–A box with a pinhole in the front and film A box with a pinhole in the front and film
paper attached to the backpaper attached to the back
–Hole prevents overlapping rays and prints a Hole prevents overlapping rays and prints a
very dim upside down imagevery dim upside down image

8. Improved lens CameraImproved lens Camera
–Lens admits more light (takes less time)Lens admits more light (takes less time)
–Allows more rays without overlapping Allows more rays without overlapping
(brighter more focused image) (brighter more focused image)

9. Explain in your own words how Explain in your own words how
this works.this works.

10. The EyeThe Eye
How do the lenses in your eyes help you How do the lenses in your eyes help you
see?see?

11. EyesightEyesight
Nearsighted – can’t see far awayNearsighted – can’t see far away
Farsighted – can’t see close upFarsighted – can’t see close up
What is the importance of the rays What is the importance of the rays
meeting at the retina?meeting at the retina?

12. Nearsighted VisionNearsighted Vision
The lens becomes shorter and fatterThe lens becomes shorter and fatter
Where do the rays come into focus?Where do the rays come into focus?
How can this be corrected?How can this be corrected?

13. Farsighted VisionFarsighted Vision
The lens becomes longer and skinnierThe lens becomes longer and skinnier
Where do the rays come into focus?Where do the rays come into focus?
How can this be corrected?How can this be corrected?

14. How are camera’s and our eyes How are camera’s and our eyes
similarsimilar

15. TelescopesTelescopes
GalileoGalileo
KeplerKepler

16. Galileo’s TelescopeGalileo’s Telescope

17. Kepler’s TelescopeKepler’s Telescope
Using a second concave lens magnified Using a second concave lens magnified
the image even morethe image even more