4th August 2011 - 1 Light lost in Reflection

In a conversation with a friend, the loss of light between two mirrors came up. That got me thinking as to why the light was lost. Was it some sort of cool quantum effect? Maybe I've been reading too much quantum stuff that I want something weird and wonderful to be happening. I went on a search for information to see if any of my ideas were in the right direction and this is what I've found so far.

In a metal, and thus mirrors with a metallic backing, light is absorbed by electrons and then re-emitted. I don't know why it's emitted at the angle it is but I think it's to do with waves but that is a question for another day. The following are reasons why the intensity of the beam diminishes.

• Some light is scattered by imperfections in the mirror, so called diffuse reflection
• Some light is scattered by the air
• Even if the mirror were perfect, some energy would be lost due to conduction between electrons

I can see I have a lot more to read up about on this topic so I'll look at it a bit more over the next few days and see if I can make any sense of it.

Sources:

Physics Forums - Loss in Mirror Reflection

Physics Forum - Light in a Mirrored Sphere

10th April 2011 Why is glass transparent?

When a photon hits brick, it takes an electron from a low energy state to a higher energy state.  It's like picking a ball up from the floor to the table.  The ball can only be on the floor or the table.  When the photon takes the electron from the 'floor' to the 'table', it is absorbed and so can not pass through.

When a photon hits glass, the excited state is way too high for the visible light photon to lift it up to that state. This means the light isn't absorbed and passes through.  The gap between the 'normal' state and the excited state is called the energy gap.

http://www.sixtysymbols.com/videos/energygap.htm