Lab Analysis Of Spectrophotometry In Chemistry

Introduction:

Spectrophotometry is a widely used method to calculate how much light is absorbed by a chemical substance. This is done by measuring the intensity of light as it passes through a sample solution. The principle of this method is that a compound absorbs or transmits light over a certain wavelength from which the measurement can be used to calculate the concentration of a known chemical substance.

A spectrophotometer is an instrument that would measure the amount of light a sample would absorb. A beam of light consists of a stream of photons. These photons, when they encounter a molecule there is a chance that the molecule will absorb the photon. This absorption thus reduces the amount of photons in the beam of light and therefore

When shone through a coloured solution, the solution absorbs some wavelengths of the white light and transmits wavelengths that are not absorbed. When we look at the coloured solution, we see the transmitted light. The transmitted light is the only wavelength that is not absorbed. For example, if a solution absorbs all wavelengths except blue, the transmitted light will be blue. The transmitted light is complementary to the absorbed colour. Complementary colours are based on the three primary colours and the secondary colours that are made by mixing two of these primary colours. When two primary colours, for example, yellow and red, are mixed together, they create a secondary colour, in this example orange, that is complementary to the third primary colour, blue in this example. This is why if only orange light is absorbed from a solution, leaving primarily blue light to be transmitted, we see the solution as blue. Similarly, a solution may appear blue if it absorbs both red and yellow

To conduct the experiment, sample solutions will be placed next to a light source, which would be a white LED, with a diffraction grating, which will split and diffract light beams in different directions, between the samples and the detector, the cell phone camera, which will be used to collect images that will then be analysed using a computer software program that measures the amount of light that will be transmitted through the sample. The same samples will then be tested in a commercial spectrophotometer to see how much accuracy there would be using a cell-phone spectrophotometer.

If high levels of accuracy are found between a cell phone spectrophotometer and a commercial spectrophotometer, this would mean that in schools where there mightn’t be the funds to purchase a commercial one, Students would still be able to conduct experiments where they will be able to find how much light can be absorbed by solutions.

Fig 2: Assembled Cell phone