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Spectrum
D. Crowley, 2008
Spectrum
To know how a spectrum (rainbow of colours) is made
Colours
What are the colours of the rainbow?
Can you make a rhyme to remember them?
RedOrangeYellowGreenBlueIndigoViolet
RichardOfYorkGaveBattleInVein
Dispersion
• White light can be split up to form a spectrum by using a prism (a triangular block of transparent material)
• Shine a ray of bright white light at a prism and move the prism until colours appear – draw a diagram showing what you have observed
Dispersion (Splitting Light)
• A prism splits a ray of white light into a spectrum of colours, known as dispersion
Waves
• What is the difference between each colour of the spectrum?
Each colour has a different wave length ()
Blue
Green
Red
Dispersion
• Why do the colours appear after they have travelled through a prism?!
• The different colours of light have different wavelengths, this means they are bent (refracted) by different amounts - which colour is refracted the most?
Red light is refracted least because it has the longest wavelength
Violet light is refracted the most because it has the shortest wavelength
Dispersion
• Light can be dispersed to give a spectrum of colours (using a prism)
• Your challenge is to recombine this dispersed light – how could you do this?
Newton’s Disc
• Spinning the disc quickly combines all the wavelengths of light – making white light via colour addition
Newton’s Disc @ Home
Colour in a paper or card circle with the colours of the spectrum
Using string or a pencil spin your disc around…
Rainbow
• In the laboratory we used a prism to split the wavelengths of light to produce the colours
• How do rainbows form in the natural world, when there are no prisms?!
• Rainbows form because of water molecules which act like miniature prisms (to see a rainbow the water droplets must be between you and the light)