A glass plate whose index of refraction is 1.56 is immersed in a ...

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A glass plate whose index of refraction is 1.56 is immersed in a liquid. The surface of the glass is inclined at an angle of 42.0 with the vertical. A horizontal ray in the glass is incident on the interface.
 
  When the liquid is a certain alcohol, the incident ray arrives at the interface at the critical angle. What is the index of refraction of the alcohol? A) 1.04
  B) 1.02
  C) 1.00
  D) 0.984
  E) 1.06

Question 2

An optic fiber is made of clear plastic with index of refraction of 1.50, surrounded by air. For what angles of incidence  will light remain within the plastic fiber?
 
  A)   21.1
  B)  < 38.3
  C)  > 38.3
  D)  < 41.8
  E)  > 41.8

[morrie123456]

Answer to Question 1

A

Answer to Question 2

E