11.3 The Ray Model of Light

November 2013,

On 11.3 we learned about the Ray Model of Light. Here’s a  short recap on what we learned from 11.3:

Figure 1

Light rays is  a line that represents the direction and path that is travelling(Figure 1). The use of light rays to determine how light behaves when it strikes objects is called geometric optics. When drawing rays, you do not need to draw it at every angle, you would only need to draw a few like the example shown in figure 1. 

Figure 2 (a) example of opaque, (b) example of transparent, (c) example of translucent

If a emitted light reflects off an object we call it incident light. when the sun emits light and the moon reflecting the light is an example of incident light. A clear material in which you can see through is called transparent . An example of a transparent object would be windows, raindrops, water. A material that transmit lights through but cannot see objects through the material is called a translucent. Example of translucent would be jello, piece of thick plastic, x-rays.  A material that does not transmit incident light is called opaque. Example of opaque is pudding, cardboard box, brick.

Flat Mirrors

Figure 2

A reproduction of an object through the use of light is called an image. Any surface that reflecting a image is called a mirror. when the light bouncing back from a surface is called a reflection. 

Mirrors are made up of two major parts: a thin layer of shinny film, that is the reflective surface, and the thick layer of glass that goes over the film to protect the film from scratching (Figure 2). 


The Terminology of Reflection

Figure 3

To illustrate how predictable the path of light is when it hits the mirror they use a plane mirror, plane meaning flat. The incoming ray that strikes the mirror first is called an incident ray (Don't get confused between incident ray and incident light). And the ray that is reflected from the mirror is called a reflected ray. The line that is perpendicular to the mirror is called a normal. The angle between the incident ray and the normal is called angle of incident. And the angle between the reflected ray and the normal is called angle of reflection. when measuring the angles, you need to make sure that the incident line is pointing to the normal. And also make sure that the normal and the mirror is perpendicular to the normal. 




If you're still having troubles understanding some parts of the lesson, here's a video that may help you understand better:

http://www.neok12.com/php/watch.php?v=zX55506f6d5e64527161720a&t=Light-Optics



By: V.E. & J.C.