1. 3.5 How does light behave when it moves from one medium to another
Name:_____________
Date:______________
Block:____

2. Refraction
Refraction causes the path of light to bend when it travels from one medium to another
Once light enters a medium, such as water, it will continue to travel in a straight line.

3. Refraction
Refraction occurs because light travels at different speeds in different media
Example: light travels at:
2.998 x 108 m/s in air
2.250 x 108 m/s in water
When light changes speed as it moves from one medium to another, the direction also changes
Incident Ray
Normal
AIR
WATER
Refracted Ray

4. Refraction
Light travels slower in a more dense medium than in a less dense medium
From this, the following are true:
When light travels from less dense to more dense mediums, the ray will bend towards the normal
When light travels from more dense to less dense medium, the ray will bend away from the normal

5. Ray Model of Light Incident Ray Refracted Ray Refracted Ray

6. Wave Model of Light

7. Refraction and the Eyes
Refraction can play weird tricks on your eyes because the eyes cannot tell that the light has bent
Your brain always assumes that light is travelling in a straight line
Penny in water activity

8. Lenses

9. What is a Lens? A lens is a curved piece of transparent material
Just like curved mirrors, a lens can be convex or concave.
A lens can cause rays to converge or diverge
The image that a lens forms depends on the shape of the lens.

10. Convex Lenses
Convex lenses are thicker in the middle than at the edge.
When light rays pass through a convex lens, they converge and come together at a focal point
Converging Refracted Rays
Parallel Incident Rays

11. Uses of Convex Lenses Magnifying glasses Eyeglasses Cameras
Microscopes

12. How does a convex lens form images?
Image is inverted

13. Concave Lenses
Concave lenses are thinner in the middle than at the edge.
The light rays that pass through the concave lens diverge.
The rays are refracted outward, and never meet at a focal point.
Images formed are
smaller and upright
Parallel Incident Rays
Diverging Refracted Rays

14. Uses of Concave lenses Eyeglasses-to correct nearsightedness
Flashlights
Door eye