The angle of deviation becomes minimum when:

1. i₁ = r₁
2. i₁ = r₂
3. i₁ = i₂
4. r₂ = i₂

i₁ = i₂

Reason — The angle of deviation becomes minimum when angle of incidence (i₁) becomes equal to the angle of emergence (i₂). This phenomenon occurs when the light ray inside the prism is incident at the minimum deviation angle and is known as the angle of minimum deviation.