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# Why do mirrors reflect and glass transmits? watch

1. So, objects are opaque because they absorb certain frequencies of light, right? The object then has colour due to reflection. However, no photons have passed through, presumably because they have to interact with particles in the many layers of atoms in some way.

If this were the case, surely glass should reflect all light? It doesn't absorb visible light, but it transmits through. Why do other objects not transmit light when glass can? Both mirrors and glass absorb little light, yet one reflects while the other transmits.
2. (Original post by ambershell27)
So, objects are opaque because they absorb certain frequencies of light, right? The object then has colour due to reflection. However, no photons have passed through, presumably because they have to interact with particles in the many layers of atoms in some way.

If this were the case, surely glass should reflect all light? It doesn't absorb visible light, but it transmits through. Why do other objects not transmit light when glass can? Both mirrors and glass absorb little light, yet one reflects while the other transmits.
I think you've detected that a lot of stuff gets glossed over at A level

If you're looking for something to read that should be accessible to an A level student there's 'QED' by R. Feynman
3. Yeah I know it's not in the syllabus but I wasn't really sure where to post and I can't find satisfactory answers online. Thanks for the recommendation though!
4. (Original post by ambershell27)
So, objects are opaque because they absorb certain frequencies of light, right? The object then has colour due to reflection. However, no photons have passed through, presumably because they have to interact with particles in the many layers of atoms in some way.

If this were the case, surely glass should reflect all light? It doesn't absorb visible light, but it transmits through. Why do other objects not transmit light when glass can? Both mirrors and glass absorb little light, yet one reflects while the other transmits.
To reply your question having regard to the photons of light, you must understand that a mirror consists of metals, aluminium or silver. Those metals have the property of reflection, because the electrons inside are stimulated by photons when they interact with those light particles. As you surely know the electrons reach a higher energy level and come back to the lower one after a short time. When they come back, the electrons emit waves of light what causes the reflcetion.

Glasses do not have this property, they can't reflect the light.
5. (Original post by Kallisto)
To reply your question having regard to the photons of light, you must understand that a mirror consists of metals, aluminium or silver. Those metals have the property of reflection, because the electrons inside are stimulated by photons when they interact with those light particles. As you surely know the electrons reach a higher energy level and come back to the lower one after a short time. When they come back, the electrons emit waves of light what causes the reflcetion.

Glasses do not have this property, they can't reflect the light.
So, to correct my previous post, mirrors do absorb light, but it is re emitted as visible light instead of IR like other opaque objects. That is what reflection is, in simple terms?
6. (Original post by ambershell27)
So, to correct my previous post, mirrors do absorb light, but it is re emitted as visible light instead of IR like other opaque objects. That is what reflection is, in simple terms?
here's a video explaining transmission of light

obviously it's not the full story because a very noticeable property of glass etc. is that it reflects a proportion of the photons incident on its surface and that also requires explanation.
7. (Original post by Joinedup)
here's a video explaining transmission of light

obviously it's not the full story because a very noticeable property of glass etc. is that it reflects a proportion of the photons incident on its surface and that also requires explanation.
Yeah, that pretty much sums up what I was thinking (we have learned about energy gaps). The reflection in glass, I thought, may be high frequency photons close to UV being absorbed. Although that doesn't really explain how it reflects all colours by a small proportion.

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