InterviewSolution
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InterviewSolution
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A rectangle glass wedge (prism) is immersed in water as shown in figure E-a. For what value of angle alpha, will the beam of light, which is normally incident on AB, reach AC entirely as shown in figure E-b. Take the refractive index of water as 4/3 and the refractive index of glass as 3/2. |
Answer» Solution :From the geometry of figure E-b it is clear that, the angle of incidence on the side BC is equal to `alpha` (dotted line is a normal DRAWN at the point of incidence). The ray should undergo total internal reflection to REACH AC. For occurrence of total internal reflection, the value of `alpha` must be greater than the critical angle at interface of WATER and GLASS.  Let .C. be the critical angle of interface of glass and water. From the GIVEN condition `alpha gt C .......(1)` We know, `sin C=1/(n^(12))` ........(2) `n_(12)=3/2 / 4/3=9/8` From equation 2, we get `sin C=8/9 rArr C=62^(@)30^(1)` Hence `alpha` is greater than `C=62^(@)30^(1)` Let us see few activities of total internal reflection. |
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