Download Simple Light Properties

Simple Light Properties
[5]
Straight Line Propagation








The straight line travel of light is known as rectilinear propagation.
The rectilinear propagation of light can be modeled as a stream of light
“particles” … the direction of travel of the particles shown as a ray.
Rays are lines drawn to show the direction that light is traveling in.
Beams are simply bundles of rays.
A stronger light source is producing a greater number of light rays.
A point source of light is a light source that emits light equally in all
directions [a tiny filament globe approximates a point source]
Lenses and mirrors can be used to produce rays of light that can converge or
diverge and lasers can produce parallel light rays.
Light from a distant light source, such as the sun, can be considered as
providing parallel rays of light
Reflection

Light is reflected off a shiny or mirrored surface.

The Law of Reflection states that the angle of incidence ( i ) = angle of
reflection ( r ) , with the incident ray and reflected ray in the same plane.

When light reflects off a flat polished metal surface [like a mirror], the reflected
rays remain parallel.
This is called regular or specular reflection and a clear image can be formed.




When light is reflected off an irregular or roughened surface, it is scattered
in all directions and a clear image cannot be formed.
This is called diffuse reflection.
In diffuse reflection, the law of reflection still holds … it’s the uneven surface
that has the reflected rays going all over the place.
Reflection, Absorption and Transmission


When light hits a surface, 3 different processes can occur … reflection,
absorption and transmission.
The amount of reflection, absorption and transmission of light depends on the
material that the light is shining on.

Opaque materials (wood, brick, rubber, plaster etc.) do not let any light pass
through them ( no transmission ); some of the light hitting the opaque material
is reflected, the rest is absorbed.

Transparent materials (water, glass, Perspex, plastic food wrap etc.) allow a
significant amount of light to be transmitted through them, some light is
absorbed and some is reflected.
Some transparent materials distort the path of the transmitted light, scattering it
and creating a frosted effect … translucent materials such as in pearl light
globes and shower glass.
No material is perfectly transparent, some light is always reflected and absorbed.
When light energy is absorbed, the temperature of the material rises.



transparent
translucent
opaque