Law of Reflection

A light ray incident upon a reflective surface will be reflected at an angle equal to the incident angle. Both angles are typically measured with respect to the normal to the surface. This law of reflection can be derived from Fermat's principle.

The law of reflection gives the familiar reflected image in a plane mirror where the image distance behind the mirror is the same as the object distance in front of the mirror.

Index

Reflection concepts

Mirror concepts
 
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Fermat's Principle:Reflection

Fermat's Principle: Light follows the path of least time. The law of reflection can be derived from this principle as follows:

The pathlength from A to B is

Since the speed is constant, the minimum time path is simply the minimum distance path. This may be found by setting the derivative of L with respect to x equal to zero.

Fermat's Principle for Refraction
 Index

Reflection concepts

Mirror concepts
 
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Fermat's Principle and Refraction

Fermat's Principle: Light follows the path of least time. Snell's Law can be derived from this by setting the derivative of the time =0.

Fermat's Principle for Reflection
 Index

Reference
Meyer-Arendt
 
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