Introduction to Optics

Introduction to Optics – Study Notes

1. What Is Optics?

• Definition: Optics is the branch of physics that deals with the behavior and properties of light (electromagnetic radiation in the visible, infrared, and ultraviolet ranges) and its interaction with matter.
• Main Goals
  • Explain how light propagates.
  • Describe how light is reflected, refracted, diffracted, and absorbed.
  • Design systems that control light (lenses, mirrors, fiber optics, lasers, etc.).

2. Fundamental Concepts

3. Types of Optics

4. Geometrical Optics

4.1 Laws of Reflection

1. Incident ray, reflected ray, and normal lie in the same plane.
2. Angle of incidence equals angle of reflection: (\theta_i = \theta_r).

4.2 Laws of Refraction (Snell’s Law)

[ n_1 \sin \theta_1 = n_2 \sin \theta_2 ]

• (n_1, n_2) – refractive indices of the two media.
• (\theta_1) – incident angle; (\theta_2) – refracted angle.

4.3 Mirrors

• Plane Mirror: Image is virtual, upright, same size, located behind the mirror at the same distance as the object.
• Spherical Mirror:
  • Concave: Real or virtual image depending on object distance.
  • Convex: Always virtual, upright, reduced.
• Mirror Equation: (\frac{1}{f} = \frac{1}{d_o} + \frac{1}{d_i})
  (f = focal length, (d_o) = object distance, (d_i) = image distance)

4.4 Lenses

• Thin Lens Approximation: Thickness ≪ focal length.
• Lens Types: Convex (converging) and concave (diverging