1. Lenses

2. OBJECTIVE
CONTRAST WAYS IN WHICH LIGHT RAYS ARE BENT BY CONCAVE AND CONVEX LENSES
[COS 5 SAT 10]

3. LENSES DEFINITION: Part of the eye that can focus light
A piece of clear glass or plastic that bends light rays passing through it
Part of the eye that can focus light
The lens is found behind the pupil. It bends light that enters the eye.

4. LENSES
THERE ARE 2 TYPES OF LENSES:
1. Convex Lenses
Concave Lenses

5. CONVEX LENS A convex lens is thicker in the middle than at the edges.
When light passes through a convex lens, the rays bend toward each other.
It makes nearby objects look bigger.
Have everyone look through a magnifying glass to verify that things already close look bigger.
Can also look through a 2 liter bottle or clear jar with water inside to magnify.

6. CONVEX LENS People sometimes need lenses to help them see better.
What are people called who need convex lenses?
Farsighted – these people have trouble seeing up close.
They wear glasses or contacts that are thicker in the middle than at the edges. Glasses or contacts with convex lenses magnify the print, allowing these people to read more easily.

7. CONVEX LENS
Besides glasses and contacts, can you name other convex lenses?
MOVIE PROJECTOR
Did you know that the light rays bent by a convex lens all meet at one point then cross, making the image on the screen appear upside down. So slides or movie film must be put into the projector upside down.
For the telescope, you can hold 2 magnifying glasses in each hand and look through them to create a telescope. Binoculars are like 2 telescopes stuck together, so each eye has its own telescope.
SLIDE PROJECTOR
TELESCOPES
BINOCULARS

8. LENSES
THE SECOND TYPE OF LENS IS KNOWN AS A CONCAVE LENS.

9. CONCAVE LENSES The lens is thicker around the edges than in the middle
When light rays pass through a concave lens, they bend away from each other.
This makes distant objects seem nearer and smaller.
Exp: camera viewfinder

10. CONCAVE LENSES
Concave lenses help people who are nearsighted. These people have trouble seeing distant objects.
Concave lenses bend light rays outward just enough to make distant obj. seem closer.
A dentist uses concave lenses

11. CONTRAST LENSES CONCAVE LENSES CONVEX LENSES
Thicker around the edges than in the middle
Help nearsighted people
When light rays pass through a concave lens, they bend away from each other.
CONVEX LENSES
Thicker in the middle than at the edges
Help farsighted people
When light passes through a convex lens, the rays bend toward each other.

12. Advantages of Lenses
Lenses allow high magnification when they are used in microscopes or telescopes.
They are also used in cameras and powerful spotlights
Lenses have opened a whole new world to scientists
Lenses can lead you out beyond the Earth, to the farthest reaches of the galaxy

13. OBJECTIVE
CONTRAST WAYS IN WHICH LIGHT RAYS ARE BENT BY CONCAVE AND CONVEX LENSES

14. CONTRAST LENSES CONCAVE LENSES CONVEX LENSES
Thicker around the edges than in the middle
Help nearsighted people
When light rays pass through a concave lens, they bend away from each other.
CONVEX LENSES
Thicker in the middle than at the edges
Help farsighted people
When light passes through a convex lens, the rays bend toward each other.

15. LENS WRAP UP
QUESTIONS
SUGGESTIONS ON MAKING THE PRESENTATION MORE EFFECTIVE