Individual work part 1: Why does light reflect different in different materials?

In this chapter I will explain using partly my own thinking combined with several resources available the different reflection of light in different materials.

First hypothesis

I think the different bondings of the atoms/ions makes the interaction different. Atoms/ions all contain electrons,protons (and neutrons). So the different interactions should be related to the way these electrons,protons (and neutrons) are structured. 

I know how light is reflected by metal. The metal bond has the electrons flow through the metal, when light interacts with the electrons in the metal, these electrons start to "vibrate" (or flow) which creates an electricmagnetic field. This field bounch of the light in the direction it came from. The flatness of the surface determines the direction of the reflection.

What I need to know is:

What is the interaction of light with molecules?

The molecuuls have a different kind of bounds (covalent bonds) which do not have a free flow of electrons. This doesn't make it possible to create this (thick) electricmagnetic field and bounce of the light on the surface. The waves penetrate deeper in the material and on their way some of them are bounced of early and some are bounced of later. Other wavelenghts can be absorbed. So for example a white object reflects all the visible wavelenghts, but on a different level of molecuul layers. This makes a white car not the same as a mirror which also reflects the image.

In really flat surfaces you can see some reflection because a percentage of the light is reflected in the same direction forming a picture like a mirror. 

references:

MIT School of Engineering. 2014. Why doesn’t a plain, white piece of paper reflect light, but a mirror does? | MIT School of Engineering. [ONLINE] Available at: http://engineering.mit.edu/ask/why-doesn%E2%80%99t-plain-white-piece-paper-reflect-light-mirror-does. [Accessed 09 December 2014].

NCBI Bookshelf. 2014. Covalent Bonds - Molecular Cell Biology - NCBI Bookshelf. [ONLINE] Available at:http://www.ncbi.nlm.nih.gov/books/NBK21595/. [Accessed 09 December 2014].

Reflection of Light. 2014. Molecular Expressions Microscopy Primer: Light and Color - Reflection of Light. [ONLINE] Available at:http://micro.magnet.fsu.edu/primer/lightandcolor/reflectionintro.html. [Accessed 09 December 2014].

Individual work part 2: Summary Reflection and transmission – quatum Behaviour – Richard Feynmann

The lecture of Richard Feynmann explains the behaviour of material by reflection and transmission according to quatum behaviour. The theory explains the cohesion between the percentage of reflection and the thickness of the material. As you see in figure 1 the percentage of reflection varies with the thickness of the material and can be 0%. This phenomena is explained by the probability amplitude (see figure 2). The arrow turns quickly around making the virtual circle drawn around it. The speed of turning depends on the color of the light involved, this is visible in figure 1 red light turns faster than blue light, because it goes through the different stages quicker.

Figure 1  Figure 2

So now we know that these arrows as in figure 2 cause the amount of reflection and refraction, we can include the thickness. When the material becomes thicker the time it takes for the light to travel through the material also becomes longer. This means that the arrows of the "layers" in the material are standing in different positions. To get to know what the influence of the arrows on eachother is, you may put them head to tail. The effect on can be explained in three different scenarios in figure 3,4,5,6,7 and 8.

In figure 3 you can see that the two arrows are quite far from each other, but still in the same direction. As you can see in figure 4 the sum is a little bigger, but the reflection is not optimal (about a reflection of 8% in figure 1). Looking at figure 5 the two arrows are in opposit direction of each other, this gives a sum of 0 this is the point the material will not reflect at all (see the 0% in figure 1). In figure 7 the arrows are very close to each other, which causes a high sum in figure 8 ( see the peaks in figure 1). So what you can conclude out these different setups, is that a shorter time the light needs to travel trough a material it makes it more likely to have the arrows close together. And when the arrows are closer together the sum of probability is higher, which results in more reflection.

Mirror

A mirror reflect most of its light towards the same angle as it came from, because this is the fastest way from the source to the mirror.  In this area the arrows of the probability amplitude are in the same direction which increases the amount of reflection. The reason the light does not reflect that well from another angle is because the time is longer and the arrows wil  in many different positions. It is however possible to reflect light from another angle, this can be done by "cutting" away the arrows which stand in the opposit direction. This will only work for one color, because as you can see in figure 1 the speed of the probability amplitude is faster or slower with different colors and the arrows will stand in different positions. 

I the lecture there were some other examples given, but I  think I have described the main point now. For the complete lecture see: