The word rectilinear literally means “straight” in Geometry and the rectilinear propagation of light means that light travels from the source in a straight line. Due to this property, light does not bend due to which we are unable to look around the corner of objects where the light ray falls upon.
There are two notable phenomenons related to the rectilinear propagation of light- reflection and refraction. Reflection can be demonstrated using a mirror and refraction can be explained when a person puts his hand inside a tub of water, the hand appears bent and smaller. Let’s perform an experiment to understand the rectilinear propagation of light better.
Experiment
Take three pieces of cardboard and pierce a hole through each of them at the same point in such a way that when the three of them are kept together, the three holes are in the same straight line. Now, the cardboards have to be set up on a table at a regular distance between them. Then take a candle that is of the same height as the distance between the tabletop and the hole in the cardboard. Light the candle and observe.
When seen from the hole of the last cardboard, the flame of the candle can be seen through the straight line of holes. But if the position of any of the cardboards is slightly disturbed and a hole is moved away from its position then the light from the candle flame will not be able to travel through and it will not be seen from the other end.
This experiment shows that light travels in a straight line. It also shows that light cannot travel through an opaque medium. Let’s take another example to show that light can travel through other transparent mediums such as water.
Take a glass of water and put a part of one of the fingers in the water. It will be seen that the finger is still visible but it is bent and appears to be smaller. This phenomenon is known as the refraction of light that causes light to bend in such a way that it creates an illusion of a raised body or a shorter hand in the water. Another natural instance of this phenomenon is the twinkling of stars in the sky. The light from the stars suffers refraction in the atmosphere due to difference in densities of the different layers of the atmosphere due to which the star appears to be twinkling even when they do not.
To know more about the rectilinear propagation of light and the various other phenomena associated with it, visit ‘s website and get free study material and resources or download the app for easy access where you will get everything you need.