I and my friend James wanted to find out the absorption capacity of different color pigments mixed in water, when exposed to the infra-red radiation. Our hypothesis was the dark color pigment, on being subjected to infra-red radiation, would absorb more energy and will show up in the form of difference in temperature obtained before and after the exposure. Our experiment was influenced by some of the experiences in daily life. First observation was the preference of the light color clothes in hot day, as the light color reflects the sunlight and absorbs the little, preventing the body from overheating. Second logic was the light coloured cars sold in the hot regions as the color of car reflects the most of the sunlight falling on it, keeping the interior not too hot. We found the similar logic of cooling in the white roof tops on the building in the south, and the blue outline texture of the swimming pools.
Now it was time to validate our hypothesis with the experimental results. For conducting experiment, we needed several ingredients- Styrofoam cups for holding water with pigments, a graduated cylinder for measuring water, source of infra-red light, an electronic thermometer to record temperature, water colors and the food colors.
The experiment began with water at room temperature, but we didn’t get the desired difference in temperature. So, we took water at 12 degree Celsius and we found the significant difference in temperature of water. Subsequently, we added different pigments-red, black, blue, yellow- and stirred it constantly. Subsequently, the pigments mixed in water were exposed to infra-red radiation for 300 seconds (or five minutes) and the initial & ending temperatures were noted down. Finally, we plotted the data on a graph and we got the following graphical representation.
In the graph above, the initial temperature and ending temperature for different pigments of water color and food color are compared. Food color section is further divided into two parts- thermometer at rest and stirring. The blue histogram indicates initial temperature and red, the ending temperature of a particular pigment. Temperature is shown on y- axis and different pigments on x-axis. The graph suggests that the biggest rise in temperature of watercolour is exhibited by red. The biggest gap in the food color category belongs to yellow (resting thermometer) and black in stirring category.
The next step was to find the variation in the temperature based on the same pigment based upon the type. The data was plotted as per color wise and we got the following graphical representation.
In the above graph also, the difference in temperature is plotted on y-axis and type of pigment on x-axis. The colour of histogram indicates the type of pigments- blue for watercolour, green for food color (resting) and red for food color (stirring). The graph clearly shows that the biggest increase in temperature for water color is noticed in red. Similarly, the biggest gap in food color (resting) belongs to yellow and black has the highest rise in temperature from food color (stirring).
The analysis of the results supported our hypothesis but only partially. We expected the dark color black to show the biggest rise in temperature, absorbing the maximum infra-red radiation in all categories. But in the cases of water color and food color (resting), our claim didn’t get the support from the experimental data. Having found the discrepancy in our experiment, I and my friend tried to find the drawbacks in the experiment. The first shortcoming was with the source of infra-red radiation. We later discovered that we used the infra-red radiation producing dull bright orange light, which is not sensitive to color. Instead, shortwave and ultra-violet wavelength radiation coming from the emitter would have produced a better result as it is more sensitive to colours. The second demerit was with the water color we used; it is made of different chemicals, unlike food color. This also might have affected the color absorption ability. Another mistake we made was not stirring the water throughout the experiment. Besides this, cold water, instead of water at room temperature, in the first instance would also have also led to better results. Finally, we thought that using different color of fabric, instead of pigments mixed in water, could also have resulted in success of our hypothesis.
Conclusion
Though the experiment didn’t succeed to prove our hypothesis, I learnt a very big lesson about the scientific temper. I came to realise that the results can go wrong due to several reasons. This does not mean the failure of efforts. It is the beginning of the discovery of several methods that will not give the desired result. The positive outcome of the experiment has taught me a lot about the infra-red radiation of different kinds and its absorption by different color pigments. At the end, it was a pleasant experience to team up with my friend James, who has lots of ideas.
