For an equilateral prism, the angle of the prism (A) is 60∘. If angles of incidence ( i ) and emergence (e) are both 70% of A, then i=e=0.7×A=0.7×60∘=42∘ The angle of minimum deviation (δm) occurs when the light path inside the prism is parallel to the base, which implies that i=e Since, i=e, we have δm‌=i+e−A ‌=42∘+42∘−60∘ ‌=84∘−60∘ δm‌=24∘ The angle of minimum deviation is 24∘.
