Back to Directory
NEET PHYSICSEasy

A ray of light is incident on a 60∘60^{\circ} prism at the minimum deviation position. The angle of refraction at the first face (i.e., incident face) of the prism is:

A

zero

B

30∘30^{\circ}

C

45∘45^{\circ}

D

60∘60^{\circ}

Step-by-Step Solution

  1. Prism Geometry: In a prism, the angle of the prism (AA) is related to the angles of refraction at the two faces (r1r_1 and r2r_2) by the equation: A=r1+r2A = r_1 + r_2.
  2. Minimum Deviation Condition: At the position of minimum deviation, the light ray passes symmetrically through the prism. This means the angle of incidence is equal to the angle of emergence (i=ei = e), and the angle of refraction at the first face is equal to the angle of incidence at the second face (r1=r2r_1 = r_2).
  3. Calculation: Let r1=r2=rr_1 = r_2 = r. Substituting this into the prism geometry equation gives A=2rA = 2r, or r=A2r = \frac{A}{2}.
  4. Conclusion: Given that the prism angle A=60∘A = 60^{\circ}, the angle of refraction at the first face is r=60∘2=30∘r = \frac{60^{\circ}}{2} = 30^{\circ}.
Practice Mode Available

Master this Topic on Sushrut

Join thousands of students and practice with AI-generated mock tests.

Get Started