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JEE Main202623 January 2026Morning ShiftPhysicsRay OpticsActual

Consider light travelling from a medium A to medium B separated by a plane interface. If the light undergoes total internal reflection during its travel from medium A to B and the speed of light in media A and B are 2.4 10⁸ ~m / s and 2.7 10⁸ ~m / s , respectively, then the value of critical angle is :

Options

  1. A⁻¹ ( 8 9 )
  2. B⁻¹ ( 9 8 )
  3. C⁻¹ ( 3 13 )
  4. D⁻¹ ( 8 17 )

Correct answer

D. ⁻¹ ( 8 17 )

Step-by-step solution

The refractive index of a medium is inversely proportional to the speed of light in that medium, given by n = c v . For light travelling from medium A to medium B , the critical angle _c is defined when light travels from a denser to a rarer medium. Given speeds are v_A = 2.4 10^8 m/s and v_B = 2.7 10^8 m/s. The refractive indices are n_A = c v_A and n_B = c v_B . The critical angle _c is given by _c = n_B n_A = v_A v_B . Substituting the values: _c = 2.4 10^8 2.7 10^8 = 24 27 = 8 9 . To find the value in terms of

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