Edexcel A-Level Physics Critical Angle

Practise Edexcel A-Level Physics critical angle through refractive-index ratios, glass-water and core-cladding boundaries, uncertainty ranges and ray diagrams.

Exam points

calculate critical angle from refractive-index ratios at glass, water or cladding boundaries
use measured critical angle and uncertainty to find possible refractive-index ranges
explain how changing cladding refractive index changes the critical angle in fibres

[Maximum number: 5]

A student determined the refractive index of a transparent material. The student had a semicircular block of the material as shown.

Figure for Question 2.3.46 - Critical angle question 1 — Edexcel A-Level Physics AS

(a)

Complete the diagram to show the critical angle.

[ 1 ]

(b)

Determine the refractive index of the transparent material, using measurements from the diagram.

Refractive index =

[ 2 ]

(c)

The student repeated the process for a second semicircular block of a different transparent material. Her measured critical angle was $C=41.0^\circ\pm0.5^\circ$ . Calculate the range of possible refractive-index values.

[ 2 ]

Use $n=1/\sin C$ at the limiting angles. For $C=40.5^\circ$ , n=1.54; for $C=41.5^\circ$ , n=1.51. Thus the possible range is approximately 1.51 to 1.54.

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2.3.46 - Critical angle question 1

Question (a)

Question (b)

Question (c)