Geometric Optics

Geometric optics calculators and formulas for refraction, reflection, and lenses. Covers Snell's law, focal length, and lens magnification calculations.

11Formulas

All levels Difficulty

Updated Jul 2026

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Fundamental

Combined Focal Length of Two Thin Lenses in Contact

1/f_combined = 1/f1 + 1/f2

Fundamental

Angular Magnification (Simple Magnifier)

M = 25cm / f

Fundamental

Depth of Field (Simplified)

DOF ≈ 2*N*c*s² / f²

Fundamental

Numerical Aperture

NA = n * sin(θ)

Fundamental

f-number (Focal Ratio) of a Lens

N = f / D

Fundamental

Brewster's Angle

θB = arctan(n2/n1)

Fundamental

Lensmaker's Equation

1/f = (n-1) * (1/R1 - 1/R2)

Fundamental

Magnification (Lens or Mirror)

m = -d_i / d_o

Fundamental

Mirror Equation (Spherical Mirror)

1/f = 1/d_o + 1/d_i

Fundamental

Thin Lens Equation

1/f = 1/d_o + 1/d_i

Fundamental

Snell's Law

n₁sinθ₁ = n₂sinθ₂