I have noticed that sometimes on a hot day, while travelling, I will see a water puddle on the road a little far away but when the car reaches there, there is no puddle or water.
I tried searching about this but couldn’t really understand why light changes its direction and we perceive it as a virtual image which looks like water.
I would really like to understand why this really happens.
Thanks!
In: 2
Why does water look like water?
Water is clear, but it has a different index of refraction than air. That means that light will refracts, or bends, when it enters the water.
That is exactly what’s happening here, but with another layer of air.
The sun doesn’t heat the air directly, it heats the ground, and the ground heats the air. On particularly hot days, the air right next to the ground is hot enough that it’s index of refraction changes. This is also why you may see wavy air over a hot grill or car engine.
When you are far away from it, the light that hits your eyes from where you see the “puddle” is traveling at a very shallow angle. This shallow angle means that the hot air is able to refract the light in a very similar way that water would, so it looks like shimmering water. When you get close, the angle changes, so the illusion stops.
This effect also has a name, it’s a mirage. You may have heard of it in a cartoon when characters are traveling through a desert, but they tend to exaggerate it to see plant life, or maybe buildings, but that’s more akin to a hallucination. A mirage is just this phenomenon making an illusory puddle of water.
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