Science Questions

What’s happening at a molecular level when a mirror is reflecting light?

Sun, 22nd Jun 2008

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Question

Connor, Tillingham. asked:

What’s happening at a molecular level when a mirror is reflecting light? I’ve looked up some articles but it doesn’t explain what exactly is happening.

Answer

One way of looking at it is that most mirrors are made out of something that conducts like a metal.  When the light, called an electromagnetic wave, that means that it had an electric field which is oscillating and vibrating.  When this light hits the metal – because it’s an electric field it means the electrons which are free to move inside a metal will start to vibrate backwards and forwards.  If electrons are moving backwards and forwards this means an electron moving backwards and forwards will create a vibrating magnetic field.  That’s how you create light in the first place.  You create another electromagnetic wave. The way in which they’re moving by the light hitting the metal will cause light to be emitted in the opposite direction.  It will reflect off in the way you’d expect light to reflect off a mirror.  Light comes in, causes electrons to move which then re-radiate the light out again as the reflected light comes off again.

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