I'm an A-level student and I love learning new things in physics. A new concept that I learnt says that the reflection is due to the scattering of light by electrons in the material. I've got my head around this yet something that bothers me is how do shiny surfaces like a mirror or reflective surface like silver or platnum reflect almost all of the light that it receives and yet certain other metals don't. If it depends on the electrons scattering light, why is the material or composition of electrons so important? What is the property that makes reflective surfaces the way that they are even when the number of electrons differs?
[Physics] Why do shiny surfaces reflect more light than other surfaces
quantum mechanicsreflectionscattering
Related Solutions
The reflection could be viewed as a two step process. The incident wave causes the electrons in the silver to vibrate like in an antenna. Though by vibrating they also emit the same light. So it's the electrons at the surface of the silver that reflect the incoming wave. As you mentioned the wave is part electric and part magnetic, but these cannot be taken apart since they are each others cause and effect: without one the other wouldn't be there either, and therefore it must reflect both parts.
That silver (and all metals) don't distort is due to the fact that they are also very good conductors. This prevents the electromagnetic waves from entering the object. The boundary conditions which must hold (from being an conductor) result in the perfect reflection and that the resulting angle is equal to the incident angle.
Similar boundary conditions are there for non-conducting materials like plastic and glass. These similar conditions result in reflection of glass and the shine/reflection on other smooth surfaces (though there can be other causes too). Also Snell's law would follow from these boundary conditions.
In contrast to conducting materials it is possible for electromagnetic waves to enter non-conducting objects. As a consequence part of the incoming wave is transmitted into the material. The propagation or dampening of the wave through the material is largely dependent on the properties of the material. Some materials like glass hardly dampen the wave and you can see through them, while others like most plastics dampen them and thus are opaque.
That's a good question. Without realising it you have stumbled across the Huygens-Fresnel principle.
The starting point it that a single silver atom is far smaller than the wavelength of light, so any scattering from it will be isotropic i.e. it will scatter the light equally in all directions.
But suppose we have two silver atoms side by side. Each atom will scatter isotropically, so in effect we have two closely spaced emitters of light and the system behaves like a Young's slits setup. Now the light isn't simply isotropically scattered, but instead it's scattered into preferred directions. (I'm oversimplifying because two atoms would be too closely spaced to act as Young's slits, but bear with me.)
Now add lots of atoms in a row, and you get something like a diffraction grating. Add lots more to make a 2D surface, then add more layers of silver atoms below, and you're building up a system where the overall light scattering is the sum of individual scattering from huge numbers of individual silver atoms. This is basically the Huygen's construction, and if you do the sums for a surface you can show that the overall scattering is only non-zero when the angle of reflection is equal to the angle of incidence. Any optics textbook should have the calculation, or a quick Google found an example here.
Best Answer
A clean metallic surface appears shiny because it is reflecting light. The interaction is due to the conductivity of the surface of the metal.
When surface conditions change, the reflectivity is reduced. For example, a clean aluminum surface is very reflective, and aluminum coatings are used on the back side of mirrors; the glass protects the clean aluminum surface.
If the clean aluminum surface is exposed to air it will rapidly oxidize. You can test this by scratching or cutting any thick piece of dull aluminum. The oxidized layer is actually a good insulator, but is quite thin. The same holds for most other metals. If they don't tarnish, then stuff gets on the surface.