Reflection of Light

When you play billiards you will notice that when a ball bounces from a surface, the angle of rebound is equal to the angle of incidence. This observation is also true with light. When an incident light ray strikes a smooth surface (like a plane mirror) at an angle. The angle formed by the incident ray measured from the normal is equal to the angle formed by the reflected ray.

Law of Reflection - The angle of incidence is equal to the angle of reflection. The reflected and incident rays lie in a plane that is normal to the reflecting surface.



Note: The red line represents the normal line. The normal line is always perpendicular to the reflecting surface.

Types of Reflection (Light)

Parallel light rays (blue arrows) reflecting on a smooth surface (mirror) illustrates SPECULAR or REGULAR reflection while DIFFUSE or IRREGULAR reflection occurs when the same parallel light rays reflect on rough surface (The roughness of a surface is a matter of degree; what appears smooth to the unaided eye can be quite rough on the atomic scale) like a piece of cloth.



For regular reflection: Parallel incident light rays are reflected in one direction only and the normal are parallel with each other.

For irregular refelction: Parallel incident light rays are reflected in different directions and the normal are not parallel with each other.

However, the LAW OF REFLECTION holds true in both SPECULAR reflection and DIFFUSE reflection

Nature of Light

Theories about the Nature of Light 1. According to Isaac Newton On his Corpuscular Theory of light - light is made up of particles that travel through space on a straight line. 2. According to Christian Huygens Light is made up of waves similar to that of water waves. This is called the wave theory of light. 3. According to James Clerk Maxwell Light is that small part of the electromagnetic spectrum which affects our vision. Light is propagated in space as electromagnetic waves. This is known as electromagnetic wave theory of light. 4. The Quantum Theory was proposed by Max Planck in 1900 and advanced by Albert Einstein in 1905. This theory assumes that light is radiated in discrete packets or bundles of energy called photons, which also exhibit wave characteristics. These youtube videos will also help you review our discussion on the nature of light. Enjoy and learn! (videos courtesy of derek owens)

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Dear Students,

This blogsite was developed to keep you posted on the day-to-day classroom discussions and activities conducted in our physics class. I hope that this web-based support mechanism will help you learn physics better.

All the Best!