Follow these steps to create your own spectrum using sunlight and a prism
Materials Required:
- A glass prism
- Thick cardboard sheet
- White screen or wall
- Sunlight (or bright white light source)
Procedure:
- Take a thick sheet of cardboard and make a small hole or narrow slit in its middle
- Allow sunlight to fall on the narrow slit to create a narrow beam of white light
- Take a glass prism and allow the light from the slit to fall on one of its faces
- Turn the prism slowly until the light that comes out appears on a nearby screen
- Observe the beautiful band of colors that appears!
Understanding how white light splits into its component colors
Key Principle
Different colors of light bend through different angles as they pass through a prism. This happens because:
- Each color has a different wavelength
- The refractive index varies with wavelength
- Violet light (shortest wavelength) bends the most
- Red light (longest wavelength) bends the least
| Color | Wavelength Range | Refractive Index | Deviation Angle |
|---|---|---|---|
| Violet | 380-450 nm | 1.532 | 44.2° |
| Indigo | 450-485 nm | 1.528 | 43.5° |
| Blue | 485-500 nm | 1.523 | 42.8° |
| Green | 500-565 nm | 1.519 | 42.1° |
| Yellow | 565-590 nm | 1.517 | 41.7° |
| Orange | 590-625 nm | 1.514 | 41.3° |
| Red | 625-750 nm | 1.512 | 40.9° |
The historic experiment that revealed the true nature of white light
Newton's Prism Experiments
Isaac Newton was the first to use a glass prism to obtain the spectrum of sunlight. His groundbreaking experiments included:
Experiment 1: Single Prism
Newton passed white sunlight through a prism and observed it split into colors. When he tried to split these colors further with another prism, no additional colors appeared.
Experiment 2: Double Prism
He placed a second identical prism in an inverted position. All the colors from the first prism passed through the second prism and recombined to form white light again!
Conclusion: This proved that white light is actually composed of seven colors, not that the prism creates the colors.
How tiny water droplets create nature's most beautiful light show
Formation of Rainbow
A rainbow is a natural spectrum appearing in the sky after a rain shower. Here's how it forms:
- Sunlight enters water droplets: Each droplet acts like a tiny prism
- Refraction at entry: Light bends as it enters the droplet
- Internal reflection: Light bounces off the back of the droplet
- Refraction at exit: Light bends again as it leaves
- Dispersion: Different colors separate due to varying refraction
Fun Facts about Rainbows:
- Rainbows always appear opposite to the Sun
- Each person sees their own unique rainbow
- Double rainbows have reversed color order in the outer arc
- You can create mini-rainbows with a garden hose on a sunny day!
Visualizing the relationship between wavelength, refractive index, and deviation