In total internal reflection, when the angle of incidence is equal to the critical angle for the pair of media in contact, what will be angle of refraction?

• A

  ${180}^{\mathrm{o}}$
• B

  $0^{\mathrm{o}}$
• C

  equal to angle of incidence
• Correct answer
  D

  ${90}^{\mathrm{o}}$

Hence, the correct answer is option: 'D'.