Properties of light – The basics of reflection and refraction
When light travels through an object, it can be affected by the properties of that medium in different ways which also affect the light. For example, from the sun, light travels through the vacuum of space largely unaffected until it reaches Earth.
Upon reaching the planet it would meet with the upper atmosphere, where it then interacts with the Ozone layer.
Here in the upper atmosphere, these powerful rays are reflected back off into space AND also allowed to enter the atmosphere. This also protects us from a majority of the sun’s radiation.
What is reflection of light?
Reflection occurs when light bounces off a certain object and
The reflection of light can be roughly categorised into two types:
Specular reflection – this is light reflected from a smooth surface at a definite angle.
Diffuse reflection – this is produced by rough surfaces that tend to reflect light at many angles. You will see far more occurrences of this type of reflection in our everyday environment.
What is refraction of light?
Refraction is the bending of light. When entering into a new medium (e.g. from a vacuum to air), the path of light is bent slightly.
This is due to a property called the refractive index. It is a dimensionless measurement of the speed in which light travels through the medium in question.
You may think that the speed of light is a constant; however, the constant is actually measured in a vacuum.
In other mediums, the speed at which light travels through the medium is dependent on the medium itself.
How do different speeds result in a bending of light?
When a light is shone at a prism at a 45-degree angle, one corner of the beam will hit the surface before the other.
This means that at one instance of this event, part of the beam is released at the same time frame from the source which is both in and out of the medium in question.
This would mean that part of the beam travels faster which is inside the medium is travelling at a faster rate than that of its non-medium travelling portion of the beam.
This results in the beam angling further into the medium to account for this change in speeds, and thus resulting in refraction.
When does total refraction occur?
It is not common for total refraction to occur.
Part of the beam would not be permitted to enter into the medium and instead, would be fired back out of the medium upon impact with the surface.
As with all things, it would then follow Newton’s laws of motion and result in an equal but opposite angle of deflection away from the surface. This is what is known as reflection.