Light has different prodigious properties. One of them is that light takes the time which is extremum. It means that the time should be either minimum or maximum.

One example which will help you to imagine the core of concept is of block. Imagine a block and now drop that block in air one time and then in water other time from same height. Now, you can imagine the timing in which the block will touch the ground.

Absolutely, the block will touch ground fatser in air than in water.

Similarly, we can think in case of light. As light will simply pass in air(vaccum) but will show reflection and refraction in water due to which its time changes. This change in time is either maximum or minimum.(Except normal incidence)

And the path it will follow in air is nothing but the geometrical path and the path it will travel in water is the optical path.

We can say simply, the actual path without any liquid (refractive index) is the geometrical path and when the light travels through any medium (liquid) then its path is said to be optical path.


  1. Good post explaining refractionπŸ‘πŸ»πŸ™πŸ»πŸ™πŸ»πŸ™πŸ» let me prod a little bit here if I may with a couple of queries.. we can understand how light refracts due to density change and light speed etc. But why does light behave this way? Do we see light because of light or only because of its reflection and refraction. If so can one not see light if there is no medium to stop or obstruct it? What obstructs light in empty space? We able to look into the past when we see stars and other celestial bodies.. food for thought. Keeping up the scientific temper and to explore and challenge our intellect is quite refreshing πŸ™‚πŸ‘πŸ»πŸ™πŸ»πŸ™πŸ»πŸ™πŸ»

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    1. Hello! Your query is pertinent. Light we see is only due to its properties of reflection and refraction, it is true. But when you talk about space, my friend space is not fully empty. In space, there are gases which is invisible for us but not for photons. Due to which in space also light shows its same properties as on earth.


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