Overview

Optics is the study of light. It covers how light moves, how it bounces (reflection), how it bends (refraction), and how we see.

Core Idea

The core idea is manipulating light. By using mirrors and lenses, we can bend light to our will—making distant things look close (telescopes) or small things look big (microscopes).

Formal Definition

  • Geometric Optics: Treating light as rays (lines). Good for lenses and mirrors.
  • Physical Optics: Treating light as waves. Good for interference and diffraction.

Intuition

  • Reflection: Light bouncing off a surface (Mirror). Angle in = Angle out.
  • Refraction: Light bending when it enters a new medium (Straw looking bent in water).
  • Dispersion: White light splitting into a rainbow (Prism).

Examples

  • The Eye: A biological camera with a lens and a retina (sensor).
  • Lasers: Coherent light (all waves marching in step). Used for surgery, cutting steel, and internet (fiber optics).
  • Fiber Optics: Trapping light inside a glass thread (Total Internal Reflection) to send data across the ocean.

Common Misconceptions

  • Misconception: Objects have color.
    • Correction: Objects reflect light. A red apple absorbs all colors except red. In the dark, it has no color.
  • Misconception: Light is instantaneous.
    • Correction: It’s fast (300,000 km/s), but finite. Looking at stars is looking back in time.

Applications

  • Astronomy: Telescopes.
  • Medicine: Lasik eye surgery, Endoscopes.
  • Photography: Cameras and lenses.

Criticism and Limitations

  • Diffraction Limit: You can’t focus light to a spot smaller than its wavelength. This limits the resolution of microscopes (until super-resolution techniques were invented).

Further Reading

  • Optics by Eugene Hecht
  • QED: The Strange Theory of Light and Matter by Richard Feynman