Arham Jain

By completing this group task I was more clearly able to understand the nature of science and some of its properties, specifically: background knowledge influences how we view data, scientific knowledge is based on evidence, science presumes that the world is understandable and science explains and predicts.

When we chose this project I assumed that it will be simple to answer the question of why CDs’ reflect rainbows as I had read before that refraction causes the dispersion of white light, splitting it into the visible spectrum. So, I thought it’s the same phenomenon at play over here. But it wasn’t so simple. The idea of refraction doesn’t tell us why different colour bands our observed at different angles and under different types of light. Hence we started our own investigation to find out what’s actually happening, to find our own evidence that could explain this phenomenon to the greatest possible extent.

We broke a CD into its various parts (images are part of the report), read about them, and saw the amount of light reflected by each of them. We came to know that the layer of aluminium is the one responsible for the super fancy colours. We knew that the surface of aluminium layer is highly uneven due to its make hence reflecting light in different directions and that’s when we went on to read about interference of light.

I was assigned the task of developing the link between interference of light and the fancy rainbows, which I found very confusing but in the end, after sufficient amount of reading I was myself able to conclude that it is indeed the interference of light responsible for the phenomenon we were investigating. In this process I myself experienced that without sufficient evidence and integration with other theories, scientific knowledge cannot be developed.

While reading I came across some conflicting theories according to which, diffraction is also a cause of this rainbow. But I chose to ignore this as if this was true, in this case the only source of diffraction can be the layer of polycarbonate and i compared the amount of light and colours been reflected with the polycarbonate and without it and it was observed there was no difference. Hence I concluded that diffraction is not a possible cause of this phenomenon. Plus if diffraction was at play, it would be able to explain the difference in colours due to different angles. Hence, I was able to make a logical choice of theory to explain the phenomenon of reflection of rainbows by CDs’ by the help of enough evidence, observations and coherence with other beliefs held true.

Hence, this project made me more aware about the nature of science and how to develop scientific knowledge.

Dawn Liew

The model used to explain refraction and reflection is a compact disc rewritable (CD-R). We have observed that rainbow colours are reflected from CD-Rs, so we wanted to find out the concepts behind this phenomenon. This model relates to natural phenomena such as bending of light by water droplets to form rainbows. CD-Rs relate to lenses, in the area of refraction. Light rays are refracted in lenses to converge or diverge. This model also relates to mirrors, where reflection is a main function of a mirror. The surface of a mirror is smooth and uniform, whereas CD-Rs have bumps on its reflective surface.

Studying the CD-R and how it reflects white light back into its discrete colours could have some potential uses. For example, many coloured lights are typically either white light shining through a coloured filter, or LED bulbs that only emit light of a particular wavelength. These sort of lights are very limited, in that they can only produce one colour. By applying a similar concept to the CD-R, and reflecting white light off a similar surface, many colours can be produced. This method is also very versatile, since changing the angle can also change the colour of light reflected.

From the study of this phenomenon, I have learnt that science demands integration. The observation of rainbow colours on CD-Rs coheres to the concepts of refraction, reflection and interference of light. Also, since science demands integration, we have to ensure that our sources are reliable and that they do not contradict each other. Science explains and predicts. This is particularly true of this study, since science is able to explain why when white light is shined onto the CD-R, rainbow colours are reflected. Science can also predict the differences in reflected light observed when CD-Rs are compared with CD-ROMs and CD-RWs. By looking at the structure of each type of CD, we are able to predict the light reflected by using the concepts that we have studied earlier. This is especially useful, because we are able to study CD-ROMs and CD-RWs without needing the actual CD.

Daniel Kwik

The focus of our project is about compact discs (CDs) and how they can mysteriously give out dazzling rainbow effects on its surface. More specifically, the way a compact disc affect light to create this effect. During the course of the project, I have learnt a lot about light and what makes us see different colours. In fact, compact discs act very similarly to prisms and raindrops that create rainbows. It all has to do with light being as a wave, and when the light waves are split up, rainbow colours are created. This project relates to many concepts such as, refraction, interference, reflection and properties of light.

To better understand how a compact disc can reflect light in such a way, we took apart the disc and split it into its components which gave us evidence of what were the actual parts of the CD that causes the rainbow effect. When we did this, we learnt that almost all the components of the CD play a role in creating the effect. We also did online research to develop a better understanding for various concepts and to validate our own observations.

I was assigned the task of laying the foundations of understanding the properties of light. Because this project has to do heavily with the way light works, understanding that white light is made out of many light waves of different wavelengths is crucial to understanding how colours of the rainbow can be seen. The things that I learnt were very new to me, but I found it very interesting, and as a whole I thoroughly enjoyed learning these things.

Through this project, I have learnt that science does not only have to do with one concept per phenomena. Some phenomenon, like creating a rainbow effect, has to do with many concepts working together, each having individual roles to create the phenomenon. I find it fascinating how all these scientific occurrences (not just the one in this project) can only be made possible through a series of unrelated concepts! Because of this project, I will never look at the world the same again. Knowing that all the beautiful colours in the world is only the way it is because of the different wavelengths of light that is reflected into my eye absolutely astounds me, leaving me hungry for more. Through this project, I have learnt how enthralling science is and have redeveloped my love for it.

Ruby Chau Wai Man

What is the Nature of Science?

It serves as a guide to important features of science, which may often be overlooked.

The features are

Science has its limits
Scientific knowledge is inherently certain
Science can be done poorly and can be misused. An example is pseudoscience.
Science is a very social process. It is done by people working together.

Source: http://www.indiana.edu/~ensiweb/nos.html

What is the model used to explain and predict phenomena you are investigating?

The wave model of light and concepts such as interference, reflection and refraction of light explains how CDs seem to reflect rainbows. From this, one can see that scientific knowledge is inherently certain. The explanation to how CDs reflect light is based on various other theories, and only if we are certain about these theories that we have scientific knowledge.

How does this model relate to other models?

As Science is a very social process, models are related. The explanation to rainbows reflected off CDs can also explain how rainbows are formed (refraction of sunlight) and rainbows observed when there is oil on water (interference of light)

Does the phenomena you investigate have any social impact?

With the influx of new technology, especially the exponential rise of the power of the internet, more and more people are relying on the internet to rely data (software downloading and multimedia sharing mediums such as iTunes). Traditional methods of physical data sharing such as CDs are gradually becoming unimportant to the present digital world.

The countless CDs from previous generations cannot be just thrown away. CDs are notoriously un-environmentally friendly.

“A CD-ROM uses a variety of non-renewable and non-biodegradable materials in its production process (such as aluminium, polycarbonate, petroleum dyes, etc. (Life cycle of a CD or DVD, 2003)) resulting in unwanted CD-ROMS either filling up landfills or being incinerated releasing harmful dioxins into the atmosphere.” University of Portsmouth, School of engineering

Hence, we should try to find more uses of a CD so they do not just become trash. As we have found out, CDs can be used to explain various phenomena of light. Cheap, interesting and safe, CDs can find a new life as educational tools, used to explain phenomena of light to students