Assertion (A): The refractive index of diamond is  √6 and refractive index of a liquid is √3. If the  light travels from diamond to the liquid, it will be  internally reflected when the angle of incidence is  30°.  

Reason (R): μ =  1 / sinC, where μ is the refractive  index of diamond with respect to liquid.  


Explanation: when light travels from denser medium to lesser denser medium then total internal reflection occurs. 

sin C = 1 / n

  • C is the critical angle  
  • n is the refractive index of denser medium (here, diamond).

Therefore, the Refractive index of diamond w.r.t.  liquid  


Thus, the critical angle is 45 degrees. Therefore, TIR will not take place at 30 °.



  • Assertion is false
  • Reason is true

So, the correct answer is (d)

Correct option: (d) 

  1. Class 10
  2. Chapter 10 Class 10 - Light - Reflection and Refraction (Term 1)
Class 10
Chapter 10 Class 10 - Light - Reflection and Refraction (Term 1)

About the Author

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CA Maninder Singh
CA Maninder Singh is a Chartered Accountant for the past 11 years and a teacher from the past 11 years. He teaches Science, Accounts and English at Teachoo