3.2 – Measuring the Critical Angle and Refractive Index (Leaving Cert Physics): Flashcards

When light travels from denser to less dense medium: angle of incidence where refracted ray emerges at 90° to normal

$n = \frac{1}{\sin C}$

When angle of incidence exceeds the critical angle

Light travels from denser (glass) to less dense (air) medium

Bends away from the normal

Flat-side down on white paper

Start with a small angle of incidence, then gradually increase it

Refracted ray emerges parallel to glass surface (90° to normal)

Repeat experiment 3-4 times

Read protractor from directly above, perpendicular to scale

Higher refractive index means smaller critical angle

Ray box

Mark the path of the incident ray that enters the glass block

Keep glass block fixed after marking outline and centre