1.

A monochromatic light is travelling in a medium of refractive index n = 1.6. It enters a stack of glass layers from the bottom side at an angle theta = 30^(@). The interfaces of the glass layers are parallel to each other. The refractive indices of different glass layers are monotonically decreasing as n_(m)=nmDeltan, where n_(m) is the refractive index of the m^(th) slab and Deltan = 0.1 (see the figure). The ray is refracted out parallel to the interface between the (m – 1)^(th) and m^(th) slabs from the right side of the stack. What is the value of m ?

Answer»


Solution :`1.6 sin theta = (N - m DELTA n)sin 90^(@)`
`1.6 sin theta = n - m Delta n`
`1.6 XX (1)/(2) = 1.6 - m(0.1)`
`m xx 0.1 = 0.8`
m = 8
MATHEMATICALLY answer is 8, but this value of refractive index is physically impossible.


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