Geometric Optics
The physics of reflection, refraction, and optical lenses.
Geometric optics describes light propagation in terms of rays. It covers mirror reflection, refractive lens paths, and total internal reflection.
This unit covers Snell's Law, focal lengths, mirror/lens formulas, and magnification properties of lenses.
Key Takeaways
- •Snell's Law describes how light bends when passing between mediums of different refractive indices.
- •Total Internal Reflection occurs when light exceeds the critical angle traveling to a less dense medium.
- •The thin lens equation calculates focal, image, and object distances.
Core Concepts & Definitions
1Snell's Law of Refraction
When light passes from one medium to another, it changes speed and bends. The ratio of sines of the angles of incidence and refraction is constant: n1 * sin(θ1) = n2 * sin(θ2).
•Refractive index n = c / v_medium.
•Light bends toward the normal when entering a denser medium (higher n).
2Thin Lens Equation
Calculates focal properties of convex (converging) and concave (diverging) lenses.
•1/f = 1/do + 1/di.
•Focal length f is positive for convex lenses, negative for concave.
Quick Revision Notes
- •A real image has positive di (can be projected on a screen); a virtual image has negative di.
- •Magnification m = -di / do. A negative m indicates an inverted image.