Notes on Colors and Light

Introduction to Colors and Light

• Focuses on the nature of color and the process of how we perceive them.

Fundamental Concepts

• Sound & Light
  • The only thing we can hear is sound.
  • The only thing we can see is light.

White Light and Colors

• White Light
  • White light is not a single color.
  • It comprises a mixture of seven colors of the rainbow: Red, Orange, Yellow, Green, Blue, Indigo, and Violet (ROYGBIV).
• Dispersion
  • Dispersion occurs when white light is separated into its component colors, which happens when light passes through a prism or raindrops, forming rainbows.

The Colors of the Rainbow

• The seven colors of the rainbow represented as:
  • Red
  • Orange
  • Yellow
  • Green
  • Blue
  • Indigo
  • Violet

The Spectrum of Colors

• The combination of these colors is referred to as the spectrum.
• Dispersion Mechanism
  • Light refracts, or bends, when entering a new medium such as glass.
  • This bending results in the separation of colors based on their different wavelengths.

How We See Colors

• The color we perceive depends on:
  • The material of the object.
  • The color of the light shining upon it.
• An object's color is determined by the light it reflects. For example:
  • A red book only reflects red light.

Primary Colors of Light

• Primary Colors
  • Red, Green, and Blue (RGB).
  • These can combine to form white light.
  • Other combinations include:
  • Red + Blue = Magenta
  • Blue + Green = Cyan
  • Red + Green = Yellow

Cones and Rods in the Retina

• Cones:
  • Sensitive to red, green, and blue light.
• Rods:
  • Sensitive only to black and white light.

Secondary Colors of Light

• Created by combining primary colors:
  • Red + Green = Yellow
  • Red + Blue = Purple
  • Blue + Green = Cyan
• List of Secondary Colors:
  • Yellow
  • Magenta
  • Cyan

Color Subtraction

• Understanding color subtraction explains how different colors can be absorbed and reflected:
  • If an object absorbs blue light, it reflects red and green light, which appear yellow to our eyes.
• Example: An object that reflects only red light appears red in white light.

Filtering Colors

• Filters (colored glass/plastic) can block specific colors:
  • Example: A red filter blocks green and blue light, allowing only red light to pass through.
• The appearance of colors changes with the type of lighting:
  • Under red light, a shirt might appear red and shorts appear black.
  • Under blue light, the situation reverses.

Practical Applications

• Activity Concept: Experimenting with colors, mixing lights, and testing theories about reflection and absorption.
• **Assessment Questions:
  1. How does a prism separate white light into spectrum colors?
  2. What three colors of light can combine to form any other color?
  3. Identify all secondary colors from a given list.
  4. What secondary color results from mixing red and blue?

Conclusion

• Understanding light and colors enhances our perception and interaction with the world, integrating physics with visual experience.