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Please refer to this image. The scene contains an object close to a mirror in the wall and a window, note that the reflected object is receiving more light than the object itself.

I read some articles about the Law of Reflection and the Ray Principle but did not get a straight answer on how the mirror(or my eyes) knows how to compose that virtual image in a way it appears to receive more light.

According to the definition of the Plane Mirror, the light rays do not actually pass through the virtual image, then why the virtual image is being composed with more light and who is responsible for that? The mirror? My eyes?

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This is a guess based on what I can see in your picture, but I think you're seeing specular reflection from the object in the mirror and diffuse reflection from the real object.

Reflection

This is an attempt to show what I think is happening. You get specular reflection of the light on the box and on the mirror, so the light apparently from the image is specularly reflected. By contrast the light reaching your eye directly from the box has to be diffusely reflected.

If the box is very shiny the specular reflection will be strong and the diffuse reflection weak, so the real box will look dark and the image bright. If the box is perfectly matt, e.g. if you covered it in blotting paper, there would be no specular reflection and the real box and the image would look equally bright. I'd guess the box is somewhere between perfectly shiny and perfectly matt, so the image looks a bit brighter than the real box.

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specular reflection was the missing concept, thanks –  user20668 Feb 7 '13 at 16:07

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