Why Does Light Reflect? (Waves - Physics)
Physics Made Easy
The reflection of light on a surface is a common phenomenon, so common that even physicist forget about the amazing physics involved. Under a classical physics perspective, light is an electromagnetic wave, in other words, light is an oscillating electric field.
When the light encounters the surface of a material, the electrons of that material naturally oscillate because subjected to the oscillating electric field of the incident light.
But… these electrons themselves carry a charge, thus produce their own electric field, that in turn oscillates too: that means that the electrons produce light also! We perceive that light as reflection (and refraction).
The light emitted by the electrons is produced in all directions. Many of these rays are cancelled out by destructive interference. The rays of light that survive (resulting from constructive interference give rise to the reflection (and refraction) rules.
Content of this video:
0:00 Why does light reflect? (introduction) 0:30 What is Light? 1:12 Effect of an oscillating electric field on a charge. 1:55 What is reflection? 3:06 Reflexion laws, where do they come from? 3:44 Why does light refract?
Credit: illustration of the water molecules: DiamondCoder via Wikimedia Commons, CC BY-SA 4.0. All other illustrations and music by Edouard Reny.
This video is produced and presented by Edouard Reny, Ph.D. in solid state chemistry and private tutor in Physical Sciences.
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