3.3 How does light behave when it encounters different materials and surfaces? Name:__________________ Date:___________________ Block:______

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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