1. Why does light behave the way it does with various materials?
The Ray Model of Light
Why does light behave the way it does with various materials?

2. Interacting with Light
Often without even know it, we have to alter certain situations to better see something due to light reflection.
Sometimes it’s light from the window reflecting off a computer or TV screen that prevents us from reading the screen
Most of us know the properties of light and its interaction with other materials without ever picking up a book to study it
In this section you will start to put a name and scientific reason to some of these properties

3. The Ray Model of Light
In this model, light is represented as straignt lines called rays.
We often use ray diagrams to depict how light travels in certain situations.

4. Ray Model of Light (cont’d)
As mentioned in the last slide, light travels in straight lines
It does this until it hits something
Different materials will potentially interact with the light differently

5. Transparent Materials
Some materials will let light go through and are called transparent materials.
An example of a transparent material is clear glass
Notice how the glass in this lantern
allows all of the light through

6. Translucent Materials
Some materials transmit some of the light, but not all of it and are called translucent materials.
An example of a translucent material is a frosted window pane
Notice how the glass in this lantern only
allows some of the light through

7. Opaque Materials
Materials that absorb light and reflect light, but do not transmit material are called opaque materials.
An example of an opaque material is a black piece of cardboard
Notice how the metal in the shade of this lamp does not allow any of the light through.

8. Shadows
Ray diagrams can also explain the size and location of shadows.
Sometimes shadows can be sharp and well defined like in the case of a small light source such as a small flashlight
Other times they may have less defined edges and this is caused by very bright light sources such as the sun
A shadow can have two parts:
The umbra: the part of the shadow where all of the light rays have been blocked
The penumbra: an area of partial shadow from a large light source

9. Shadows (cont’d)
This diagram illustrates the umbra and penumbra from a larger light source, the sun.

10. Light Reflection Light travels in parallel lines
When they hit a smooth surface, they will reflect off the surface parallel to one another
This is called regular reflection
When regular reflection occurs, it is
possible to see an image in the reflection.
A plane mirror is an example of such
a surface.

11. Light Reflection (cont’d)
An object can still reflect light even if it does not produce an image.
Materials that are rough will cause light to be scattered in many directions
This type of reflection is called diffuse reflection.
One can see how light reflects in
many directions off the rough surface. Though it appears smooth, the surface of the page of your textbook is rough. This allows one to see read the page from almost any angle.

12. Activity Some Properties of Light
Go to page 407 in the Pearson Investigation Science 10 textbook and do the activity Some Properties of Light.
Do questions 6 – 10. Put your answers on page 2 of the title page for this lesson.