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Light reflection

 

Light is known to behave in a very predictable manner. If a ray of light could be observed approaching and reflecting off of a flat mirror, then the behavior of the light as it reflects would follow a predictable law known as the law of reflection. 

The diagram below illustrates the law of reflection. 

The law of reflection

       When light reaches a mirror, it reflects off the surface of the mirror:

The incident ray is the light going towards the mirror

The reflected ray is the light coming away from the mirror

 


       In the ray diagram:

The hatched vertical line on the right represents the mirror

The dashed line is called the normal, drawn at 90° to the surface of the mirror

The angle of incidence, i, is the angle between the normal and incident ray

The angle of reflection, r, is the angle between the normal and reflected ray

The law of reflection states that the angle of incidence equals the angle of reflection, i = r. It works for any angle. For example:

The angle of reflection is 30° if the angle of incidence is 30°

The angle of reflection is 90° if the angle of incidence is 90°

In the second example, if a light ray travelling along the normal hits a mirror, it is reflected straight back the way it came. 

The reflection of light from a flat surface such as a mirror is called specular reflection – light meeting 

the surface in one direction is all reflected in one direction.

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