Colors of Light, Dispersion, and Spectrum

Introduction to Light Colors

• Magic bulb that changes colors via an app.
• Experiment with colored light on blocks of red, green, and blue.

Experiment Overview

• Initial Setup:
  • White light from the bulb.
  • Three blocks: red, green, blue.

Experiment Steps

1. Red Light:

   • Red block visible, green and blue blocks appear blackish.
   • Reason: Red block reflects red light, others absorb it.

2. Green Light:

   • Green block visible, red and blue blocks appear blackish.
   • Reason: Green block reflects green light, others absorb it.

3. Blue Light:

   • Blue block visible, red and green blocks appear blackish.
   • Reason: Blue block reflects blue light, others absorb it.

Conclusions from the Experiment

• Objects reflect light that matches their color and absorb all other colors.
• Example: Red block reflects red light, appears black under green and blue lights.
• White Light:
  • Composed of many colors including red, green, and blue.
  • Fact: White light contains millions of colors.

Nature of Light and Sound

• Both light and sound are forms of energy that exist as waves.
• Different colors of light have different frequencies similar to sounds.

Dispersion of Light

• Definition: Splitting of white light into constituent colors.
• Spectrum: The band of colors obtained from dispersion.
  • Simplified to seven colors: Violet, Indigo, Blue, Green, Yellow, Orange, Red.
• Examples:
  • Rainbow
  • Colors on the back of a CD/DVD.

Refraction and Dispersion

• Refraction: Bending of light when it passes through different media (e.g., air to glass).
• Monochromatic Light: Light of a single color, bends differently than white light due to varying speeds in glass.
  • Speed of light in air is constant for all colors.
  • Different colors have different speeds in glass, causing them to bend at different angles.

Use of Prisms

• Two prisms can recombine colors back into white light.
• First Prism: Splits white light into seven colors.
• Second Prism: Combines colors back to white light.

Natural Occurrences of Spectrum

• Rainbows: Formed when sunlight is split by rain droplets acting as prisms.
• Conditions for Rainbow:
  • Sun behind the viewer, rain ahead.
• Process:
  1. White light enters a raindrop.
  2. Light disperses into colors due to different speeds in water.
  3. Total internal reflection occurs, followed by refraction when leaving the droplet.

Final Thoughts

• Light is colorful; absence of colors is like an old black and white movie.

Engagement

• Top three questions for the audience.
• Encouragement to subscribe and engage with the content.