# Joint Entrance Examination/2000 Screening/Q033 Glass slab in water and total internal reflection

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# Original Question by Dharav talk

Here's the question...
 A rectangular glass slab ABCD of refractive index n 1 is immersed in water of refractive index n2 (n1 > n2). A ray of light is incident at the surface AB of the slab as shown. The maximum value of the angle of incidence α?max, such that the ray comes out only from the other surface CD, is given by... ${\displaystyle \sin ^{-1}{\frac {n_{1}}{n_{2}}}\cos \left(\sin ^{-1}{\frac {n_{2}}{n_{1}}}\right)}$ ${\displaystyle \sin ^{-1}\left[n_{1}\cos \left(\sin ^{-1}{\frac {1}{n_{2}}}\right)\right]}$ ${\displaystyle \sin ^{-1}{\frac {n_{1}}{n_{2}}}}$ ${\displaystyle \sin ^{-1}{\frac {n_{2}}{n_{1}}}}$Posted by Dharav talk 07:16, 18 August 2009 (UTC)

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