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A student very cautiously traces the path of a ray  through a glass slab for different values of the  angle of incidence (∠i). He then measures the  corresponding values of the angle of refraction  (∠r) and the angle of emergence (∠e) for every  value of the angle of incidence. On analyzing these  measurements of angles, his conclusion would be 

(a) ∠i > ∠r > ∠e 

(b) ∠i = ∠e > ∠r  

(c) ∠i < ∠r < ∠e 

(d) ∠i = ∠e < ∠r  




  • For a glass slab, light enters from rarer to denser medium, hence ray is bent towards from normal
  • Thus, angle of refraction will be less than angle of incidence
  • Then, when it comes out, light travels from denser to rarer medium, hence ray bends away from normal
  • Hence, angle of emergence is greater than angle of refraction.
  • Since opposite faces of glass slab are parallel, angle of emergence will be equal to angle of incidence


So, the correct answer is (b) - ∠i = ∠e > ∠r

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Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 13 years and a teacher from the past 17 years. He teaches Science, Economics, Accounting and English at Teachoo