Question

10(c). A ray passes symmetrically through a glass prism of angle 60° and refractive index 1.5. Calculate the angle of: (i) incidence; (ii) minimum deviation.

Accepted Answer

For symmetric passage, r=A/2=30°. Using n=sin i/sin r: sin i=1.5×sin30°=0.75, so i=sin⁻¹(0.75)≈48.6°.
For minimum deviation: n=sin((Dm+A)/2)/sin(A/2) → sin((Dm+60°)/2)=1.5×sin30°=0.75 → (Dm+60°)/2≈48.59° → Dm≈37.2°.

WAEC Physics 2021 Theory — Question 22

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