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Physics Paper 2, Nov/Dec. 2009  
Questions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Main
General Comments
Weakness/Remedies
Strength
















Question 3
Part I:      Candidates were required to answer any five questions from this part.
  1. A ray of lights is incident on an air-glass boundary at an angle θ.  If the angle between the partially reflected ray and the refracted ray is 90o, calculate angle θ given that the refractive index of glass is 1.54.

     

_____________________________________________________________________________________________________
Observation

Few candidates attempted this question and majority of those who did performed poorly.  Many candidates misconstrued the question and were calculating critical angle.

The expected answer is:

Diagram

 

 

n  =  sin θ                    =    sin θ    =  tan θ                                                      
      Sin (90 – θ)                  cos θ
                                                                                               
1.54   =   tan θ                                                                                                
θ   =    57o


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