ACTIVITY 2
Designing a Spectroscope
Introductions:
What is visible Light? Light is a form of electromagnetic radiation within the electromagnetic spectrum and only a small portion of the electromagnetic spectrum is considered visible light. The Visible spectrum (Figure 2) is responsible for your sense of sight and can therefore be detected by the eye, however most of the electromagnetic spectrum is invisible to the human eye.
We know that white light is made up of a collection of colours and each colour corresponds to a different wavelength. Light disperses according to its wavelength and the interaction with the refractive index of materials. Prisms play a large role in allowing us to separate light due to its wavelength this can be readily seen in rainbows. As the white light emitted by the sun enters a raindrop (the prism) it bends due to the refractive index of water and disperses according to its wavelength. Therefore, rainbows form due to the different colours bending in accordance to their wavelength when separated through a refractive index.
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You will be creating a spectroscope and observing different light sources. A spectroscope is a tool which can be used to analyses different materials depending on their light emittance within the electromagnetic spectrum. Spectroscopes are like prisms; however, they utilise diffraction gratings to help separate light. Diffraction gratings are an optical component in this case a CD which separates light into several beams which travel in accordance to their wavelength. Various light sources are composed of different materials and this can affect the observed emittance when analysed using a spectroscope.
Methods
Part 1: Building the Spectroscope
1. Download and print the cutting guide found at https://www.exploratorium.edu/sites/default/files/snacks/CD-Spectroscope-Cutting-Guide.pdf, cut out the template and attach it lengthways around an end of a 90mm diameter cardboard tube using tape.
2. Using a knife, cut out the black rectangle formed by the meeting edges of the template as well as the section of tube underneath. This will produce the viewing window.
3. Cut down into the tube as indicated by the line (which should now appear straight) you can now remove the cutting guide from the tube.
4. Insert the CD into the resultant slot, make sure the reflective side faces the opposite side of the tube.
5. Cut a slit around 5cm tall into one of the tube caps, making it as thin as possible. Attach cap to the tube at the opposite end to the CD.
6. Attach the other cap at the end of the tube close to the CD.
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