1. 3.3 How does light behave when it encounters different materials and surfaces?
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2. Behavior of light towards different materials and surfaces
Light behaves in different ways when it encounters different materials
Light can be: reflected, absorbed, transmitted or refracted
Elk Lakes Provincial Park

3. Reflection
Reflection is the process in which light “bounces off” a surface and changes direction
There are two types of reflection:
Reflection off an extremely smooth surface
Reflection off a rough surface
Emerald Lake in Yoho National Park

4. Reflection of a Smooth Surface
Good examples of reflection off an extremely smooth surface would include mirrors and a very still body of water
When they reflect light, the pattern of reflected rays are similar to the pattern of the incoming rays
This similarity lets you see an image when the light reaches your eye
Incoming Rays
Reflected Rays
Smooth Surface

5. Reflection of a Rough Surface
An example of reflection off a rough surface would be paper
When reflected rays hit the rough surface of the paper, they scatter in different directions
Pattern of reflected rays is not similar to incoming rays, so no image appears
Some reflected rays reach your eyes, which make the paper visible
Magnified image of paper showing rough surface
Incoming Rays
Reflected Rays
Rough Surface

6. Absorption, Reflection and Colour
Absorption is the process in which light energy is trapped in an object as heat
Why does a red ball appear red?
When white light hits an object, some colours are absorbed and others are reflected
The reflected colours are what we see!!!
Example: A red ball absorbs all colors except it reflects red back to our eyes
White Light
Red colour reflected
Rest of the colours are absorbed

7. Black and White
When you see a black t-shirt, every colour is being absorbed.
White Light
No colours reflected
All are absorbed
When you see a white t-shirt, every colour is being reflected.
All colours reflected
None are absorbed
Why do objects then look dark in a dark room?
Because there is no light to bounce off of objects.
Without light to bounce, there is no light to reach your eyes

10. Absorption, Reflection and Colour
Rays that hit the black letter are absorbed, so the letter looks black.
The blue letter absorbs all wavelengths of light except blue.
Only the blue light reaches your eye.
absorption: the process in which light energy is trapped in an object as heat

11. Mixing Colours
Mixing colours of light is not the same as mixing colours of paint.
When we mix light we mix different wavelengths, producing new unique wavelengths

12. Colour and Reflection
The colours red, green, and blue are called the additive primary colours
When these 3 colours are mixed they can produce all the colours of the rainbow
Combining the light of two additive primary colours will produce the secondary colours:
Red + Green = Yellow
Red + Blue = Magenta
Blue + Green= Cyan

13. Refraction
Refraction is the process in which light changes direction when it moves from one medium to another
Example: Light bends as it moves from air to water
Incident Ray
Refracted Ray
Air
Refracted Ray
refraction: : the process in which light changes direction when it moves from one medium to another
Water
Air

14. Transmission
Transmission is the process in which light passes through a medium and keeps travelling
When light passes through a material, that material is called a medium
Different materials transmit different amounts of light
Example: clear glass window transmits more light than a sheet of paper
transmission: the process in which light passes through a medium and keeps travelling

15. Transparent, Translucent, Opaque Materials
A material can be transparent, translucent, or opaque depending on:
How much light it lets pass through
How the light behaves
If you can see through it

16. Transparent Materials Transmit Light
Transmit almost all light rays
Objects can be seen clearly through them
Examples: clear glass, plastic, water, air

17. Translucent Materials Scatter Light
Allow most light to pass through them
Light is scattered in many directions as it passes through
Objects seen through them are blurry
Examples: frosted plastic, waxed paper

18. Opaque Materials Reflect and Absorb Light
Do not allow any light to pass through them
Objects cannot be seen through them
Examples: wood, metal, stone
Light Absorbed