Note: This post addresses the question at “GCE O Level” level.
In terms of classical wave theory, light is an electromagnetic wave that is capable of passing through free space or through a material medium in the form of varying electric and magnetic fields. In the absence of influence, the wave travels straight.
In terms of the modern quantum theory, electromagnetic radiation, such as light, is a flow of photons (“small packets of light”) through space. This means that light is made up of particles.
Particles and waves are two entirely different things. How can light be both a particle and a wave? If you are interested, check out my post on Wave particle duality and/or google for the term.
When light is incident in a perpendicular direction on the surface, such as a piece of glass, part is transmitted and part is reflected. This happens at any surface that forms the boundary between two transparent mediums of different refractive indices.
For the topic of “Reflection And Refraction Of Light”, we will only be concerned about light as an electromagnetic wave.
