Chapter 18Section 18.3 Behavior of light

Light and Materials

Without light nothing would be visible.

Light behaves differently depending on what the object is made of.• Materials can be transparent translucent or

Opaque

1. Transparent: is a material you can clearly see through.• Is a material that transmits light.• This means that most of the light that strikes the

object passes through it.• Ex: Water, windows, certain plastics

2. Translucent: is a material that you can see through, but it is not clear or distinct.• A material that scatters light.• Ex: Frosted glass, liquid soap

3. Opaque: a material that you cannot see through.• This is what most material are.• No light passes through these objects.• A material that absorbs and reflects all light

that strikes it.• Ex: Wood, metal

Interactions of Light

• Just as light can affect matter, matter can affect light

• When light strikes a new medium, the light can be reflected, absorbed, or transmitted.

• When light is transmitted, it can be refracted, polarized, or scattered.

1. Reflection is the interaction that occurs when a wave bounces off a surface that it cannot pass through.• Image is a copy of an object formed by

reflected/refracted waves of light.

There are 2 types of reflection

A. Regular reflection is where parallel light waves strike a surface and reflect all in the same direction.• This happens when light hits smooth, polished

surfaces.• You have a clear image• Ex: mirrors, calm water

B. Diffuse reflection is where parallel light waves strike a rough, uneven surface and reflect in many directions.• When it reflects from a rough surface, you

see a blurred image or nothing.• Ex. The rough surface of paper in book.

2. Refraction- when a light wave bends as it enters a new medium at an angle.• Ex: light from air to water-under water the

objects appear closer or larger than they are.• Can cause a mirage.

Mirage is a false or distorted image.• This happens because light travels faster in hot air

than in cooler, dense air.• Makes the light follow a curved path instead of a

straight path to the ground.• Ex: hot day, desert

3. Scattering- is a process by which light is redirected as it passes through a medium.• Ex: this happens in the sky as sunlight hits the tiny

particles in the atmosphere.• Scattering effect reddens the sun at sunrise and

sunset.

• Short wavelengths scatter more than long wavelengths.

• As you get higher in the sky, the light travels a shorter distance.

• Therefore, the sky is blue/colorless.

4. Polarization-is a type of light with waves that vibrate in only one plane.• Unpolarized light vibrates in all directions.• Polarized filters block waves either horizontally or

vertically.• Why we wear sunglasses to stop the glare of

polarized light.