1. Transparent substances refract light
Refraction
Transparent substances refract light

2. It’s not magic… it’s science!

3. How light Refracts Refraction is due to changes in the speed of light.
In space, light travels at km/s. Space is a vacuum, and there are no particles to get in the way of light and slow it down.
It is impossible to move at top speed when particles get in the way (think of what it is like to move through the hallway in between bells!)
If the light strikes a medium of different density at an angle, it refracts (or bends!)

4. Refraction in different media
Media or a medium means a different substance
The denser the new medium, the more the light slows down The slower the light travels, the more it will bend or refract!

5. Activity Groups of two “Pop Quiz”
(Check and Reflect Questions Page 203)

6. Lenses
Lenses refract light

7. Lenses
A lens is a piece of curved glass or other transparent material (sometimes plastic)
It is smooth and regularly shaped so when light strikes it, it refracts in a predictable way.

8. Concave lens A Concave lens is thinner in the centre than at the edges
As parallel rays pass through, they are refracted away from the centre of the lens.
The rays diverge.

9. Convex Lens
A convex lens curves outward and is thicker in the middle than at the edges.
As parallel light rays travel through, they move toward each other.
The rays CONVERGE.

10. Convex Lenses
The ability to bring light rays together is useful because:
It can act as a light collector (much like a concave mirror). This type of lens is used in a refracting telescope.
The light rays actually meet at a point and form a REAL IMAGE - the image can be projected into a screen However, it is upside down!

11. Convex lens Real image Real Image
The image appears upright and bigger, and forms on the same side as the object For example: a magnifying glass

12. Activity Concave Mirror Convex Mirror Concave Lens Convex Lens
Divide a piece of blank paper into four rectangles.
Draw and Label four diagrams showing how the rays behave when they interact with Each mirror and lens.
Concave Mirror
Convex Mirror
Concave Lens
Convex Lens

13. Activity Concave Mirror Convex Mirror Concave Lens Convex Lens
Divide a piece of blank paper into four rectangles.
Draw and Label four diagrams showing how the rays behave when they interact with Each mirror and lens.
Concave Mirror
Convex Mirror
Concave Lens
Convex Lens