Define critical angle and total internal reflection. Explain the conditions required for total internal reflection.
زاویۂ بحرانی اور مکمل اندرونی انعکاس کی تعریف کریں۔ مکمل اندرونی انعکاس کی ضروری شرائط واضح کریں۔
Solution & explanation
For n₁ > n₂, critical angle C is incidence giving r = 90°. Total internal reflection requires light travelling toward lower n and i > C. At i = C the refracted ray is grazing; it is the threshold, not strictly above it.
Independent study answer. Original textbook ↗ · English-medium printed page 87.