1. Introduction

1. Introduction
1. Background Research

We find that here are a few methods that can help us find out the concentration of sugar in sugary drinks. We can use a hydrometer to measure the density of liquids or by boiling-off method. However, the hollow prism method seems to be a very convenient and cost effective method. The Hollow Prism method works on the basis of refraction.

Refraction is the bending of light when it passes from one medium into another.

Figure 1 (Wood, 2003) (Images © Robin Wood, 2003, used with permission.)

The straws in Figure 1, above, seem to bend because of a phenomenon called refraction, the bending of a wave as it passes from one material into another. Waves travel at different speeds through different mediums (such as air and water), and this speed difference makes the wave refract when it passes from one material into another. As light waves travel from the water into the air, the wave refracts, which makes the straws in Figure 1, above, look bent or broken.

The refraction is different in the two parts of Figure 1,. The denser the medium, the slower the wave travels through the medium. The speed at which a light wave travels through a medium is quantified in the index of refraction, n, of that medium. It represents the ratio between the speed of light in a vacuum and the speed of light in the medium of interest. For example, the index of refraction of air is 1.00028, so light travels 1.00028 times faster in vacuum than it does in air.(Belay and Assefa, 2018)

These two images also illustrate refraction by liquids. The glass on the left contains plain water, and the other contains sugar-water. The sugar in the water increases the density of the water hence increases the refraction index.

We learnt that the angle of refraction, or how much a light wave bends when it travels from one medium to another, is related to the indices of refraction by a mathematical formula called Snell's Law (Kieran S. Mital, 2010). Snell's Law tells us that the greater the difference between the indices of refraction of two materials, the more the light bends.

We can determine the sugar concentration of different sugary drinks (density) by measuring the refraction of the light wave (laser) of these liquids using the hollow prism method. We will first measure the refraction of the laser of known sugar concentration water (15g/100ml, 10g/100ml, 5g/100ml). Then we will measure the refraction of laser of 6 carbonated sugary drinks. We will then compare the results with the packaging information to conclude the accuracy of this method.

We chose this as our project as we were curious on whether if there is a way to find out how much sugar is in different drinks instead of just reading the labels at the back of the can or bottle. Using this method (Snell’s Law) is also very convenient as there are not many different types of equipment needed for this experiment. The central equipment needed for this experiment is a hollow prism, a laser and the solution or sample you would like to test (Kieran S. Mital, 2010). Also, this experiment does not take much time to conduct. So, if you want to check the sugar concentration in your drink on  typical day, it can be done quickly as well as easily and would not make a mess if there is no drink spilled. We could also use this method to test the sugar concentration levels in other drinks apart from soda such as homemade fruit juices, bottled fruit juices or iced teas.