LIGHT & OPTICS · LAB 20

Refraction and Snell’s law

See how light reflects and changes direction as it crosses the boundary between two transparent materials.

OPTICAL STATEREFRACTION

Drag the source or incidence point to change the ray geometry

IncidentRefractedReflected

INCIDENT / REFLECTED42.0° / 42.0°

θᵢ = θᵣ

REFRACTED—

Snell’s law

CRITICAL ANGLE—

n₁ ≤ n₂

REFLECTED—

— transmitted

LIGHT SPEEDS—

—

WHAT TO NOTICE

Changing speed changes direction

Light bends towards the normal when it enters a higher-index medium and away from it when it enters a lower-index medium. Above the critical angle, no propagating ray enters the second material: all the light is internally reflected.

n = c / vn₁ sin θ₁ = n₂ sin θ₂θc = sin⁻¹(n₂/n₁)

Educational estimates using ideal flat boundaries and simplified unpolarised Fresnel calculations.