Introduction
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.
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FAQs on Rectilinear Propagation of Light
1. What is the Rectilinear Propagation of Light?
Rectilinear propagation of light is the natural phenomenon of light that causes it to travel in a straight line without hindrance. When the path is blocked by solid or opaque objects, light cannot travel through, and thus, there will be shadows.
2. What are some examples of the rectilinear propagation of light?
Some natural examples of the rectilinear propagation of light are:
the solar eclipse where when the moon comes between the sun and the moon, the moon covers the path of light from the sun and thus it casts a shadow.
when you stand in front of a mirror, you can see yourself which is also because of the reflection of light on the mirror.
if a stick is put in water, the part which is inside water appears to be bent but is still visible.
3. When Does the Path of Light Bend?
The path of light bends when it travels from one medium to another medium, with the latter having a different density.
4. What is refraction?
Refraction is the phenomenon of light where an object appears to be bent due to the deflected path of light when it travels to a heavier medium from a lighter medium. An example of this phenomenon is the bent appearance of a hand put in water.
5. What is reflection?
Reflection is the phenomenon of light where it changes the direction of propagation and bounces back when it falls on a smooth opaque object such as a mirror.
6. Why does the path of light bend?
Due to differences in the densities of different mediums, when light travels through the mediums, it suffers deflection of its path of propagation. Thus when it ultimately reaches our eyes after bouncing off from an object, the object appears to be bent due to the bending of the path light.
