Separating White Light into Colors
Materials: ★★☆ Available in most school laboratories or specialist stores
Difficulty: ★☆☆ Can be easily done by most teenagers
Safety: ★☆☆ Minimal safety procedures required
Categories: Light
Alternative titles: Dispersion of Light with a Prism
Summary
When white light passes through a triangular prism, it separates into its component colors (red, orange, yellow, green, blue, violet). This occurs because each wavelength of light refracts, or bends, by a different amount as it enters and exits the prism.
Procedure
- Place a sheet of white paper on a flat surface to act as a screen.
- Set up the light box with a single slit so that it produces a narrow beam of white light.
- Position the triangular prism in the path of the light beam.
- Adjust the prism angle by turning it slightly clockwise or counterclockwise until a clear rainbow spectrum appears on the paper.
- Observe the order of colors from least bent to most bent: red, orange, yellow, green, blue, and violet.
Links
Making a spectrum with a triangular prism and ray box - Physics with Simon Poliakoff:
📄 Experiment Guide (Page 27) - Edu Lab: https://s3.eu-west-2.amazonaws.com/edulabdocumentsandimages/documents/library/manuals/ESR23%20Manual.pdf
Variations
- Use different types of prisms (glass vs. acrylic) and compare the clarity of the spectrum.
- Place the prism at different angles to produce wider or narrower spectra.
- Shine colored light instead of white light to see how a prism affects a single wavelength.
Safety Precautions
- Avoid looking directly into the light box beam.
- Handle the glass prism carefully to prevent breakage.
- Keep electrical leads and power supply away from water.
Questions to Consider
- Why does red light bend less than violet light in a prism? (Because red has a longer wavelength and lower refractive index than violet.)
- What is the order of colors in the visible spectrum? (Red, orange, yellow, green, blue, violet.)
- How is dispersion in a prism related to the natural formation of rainbows? (Raindrops act like tiny prisms, refracting and reflecting sunlight to separate colors.)