Optics — Formula Sheet

Speed of light in vacuum

c = 3×10⁸ m/s

Laws of reflection

(1) Incident, reflected rays and normal are coplanar (2) i = r

Multiple images in inclined mirrors

N = 360°/θ - 1 (conditions apply)

Snell's law

n₁sinθ₁ = n₂sinθ₂

Real depth/Apparent depth = refractive index (for plane surfaces)

Same mirror formula applies to lenses

1/f = 1/v + 1/u

Lens maker's formula

1/f = (n-1)(1/R₁ - 1/R₂)

Two fundamental laws

(1) Incident ray, reflected ray, and normal lie in the same plane (2) Angle of incidence equals angle of reflection (i = r).

For spherical mirrors

1/f = 1/v + 1/u, where f = R/2 (focal length), v (image distance), u (object distance), R (radius of curvature).

At interface between media with refractive indices n₁ and n₂

n₁sin θ₁ = n₂sin θ₂.

When light travels from denser to rarer medium at angle greater than critical angle θc (where sin θc = 1/μ), complete reflection occurs.