InterviewSolution
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InterviewSolution
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(a) Define the term 'critical angle' for a pair of media (b) A point source of monochromatic light S is kept at the centre of the bottom of a cylinder of radius 15.0 cm. The cylinder contains water (refractive index =4/3 to a height of 7.0 cm. Drawthe ray diagram and calculate the area of water surface through which the light emerges in air. |
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Answer» Solution :(a) N/A (b) (b) The ray diagram is shown in Fig. 9.55. The light emerges in air along a circular surface of WATER of radius OB = R, where `angleOSB = i_( c)` = critical angle for wave-air INTERFACE.  Obviously, `sin i_( c) = (OB)/(SB) = R/sqrt(h^(2) + R^(2)) = 1/n` `rArr R = h/sqrt(n^(2)-1) = (7 cm)/(sqrt((4/3)^(2))-1) = 3sqrt(7) cm` `therefore` Area of water surface `A = piR^(2) = 22/7 XX (3sqrt(7))^(2) = 198 cm^(2)` |
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