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JEE Main 2025 Apr 3 Shift 1, Physics Q20: Prism

JEE Main2025Apr 3, Shift 1Physics
Q.

Consider following statements for refraction of light through prism, when angle of deviation is minimum.

(A) The refracted ray inside prism becomes parallel to the base.

(B) Larger angle prisms provide smaller angle of minimum deviation.

(C) Angle of incidence and angle of emergence becomes equal.

(D) There are always two sets of angle of incidence for which deviation will be same except at minimum deviation setting.

(E) Angle of refraction becomes double of prism angle.

Choose the correct answer from the options given below.

  1. A

    A, C and D Only

  2. B

    B, C and D Only

  3. C

    A, B and E Only

  4. D

    B, D and E Only

Solution

For a prism, . At minimum deviation :

(A) The refracted ray inside the prism runs parallel to the base — a symmetric passage. ✓

(B) Larger prism angles give larger (since , as increases increases too for fixed ). So (B) is incorrect.

(C) Symmetric path: . ✓

(D) The vs curve is U-shaped with a single minimum, so for any there are exactly two angles of incidence producing the same deviation; only at the minimum is the angle unique. ✓

(E) At minimum deviation each refracted angle equals ; their sum is , not . (E) is incorrect.

Correct statements: A, C, D.

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