Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: ScientificSorcerer on 29/09/2014 19:03:36
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Heat ripples when its not hot
Everybody has seen heat ripples at some point in their lives. In the form of road mirages or around bonfires or grills. It's just a very common occurrence in our every day lives.
It isn't because an object is very hot though, the ripple effect can occur without higher temperatures higher then room temperature. It's not about how hot something is, it deals only with a difference in air density. When air gets hotter it gets less dense and gets a different refraction index then cooler air. As a result light gets refracted at a different rate at different temperatures through air, when air temperature isn't evenly distributed it creates a distortion of light known as a heat ripple.
If the air was close to liquid temperature and you blew room temperature air on it then you would get heat ripples.
I wonder though, can you use another gas with a different refraction index to make the ripple effect without the need for a difference in temperature?
What I mean is, can you put a less dense gas like helium in the air at the same temperature to make a ripple effect like heat waves do?
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Yes, absolutely! Through it is much easier to see the effect when using a gas substantially denser than air. You have to get something that has a very different refractive index than air to see this though. The most obvious example for me is when pouring a volatile organic solvent (like diethyl ether or dichloromethane)--one can really see the ripples pour out of the bottle before the liquid makes it out. You can also just barely make out some ripples from letting the butane out of an unlit cigarette lighter (just hold the button down without sparking it).