1.

A parallel beam of white light falls on a thin film whose refractive index is 1.33. IF angle of incedence is 52^(@) then thickness of the film for the reflected light to be coloured yel,ow (lambda = 6000 Å) most intensively must be :

Answer»

`14(2N + 1) mu m`
`1.4(2n + 1) mu m`
`0.14(2n + 1) mu m`
`142(2n + 1) mu m`

Solution :`mu = (sin i )/(sin R)`
`therefore sin r = (sin i)/(mu) = 0.6`
`therefore cos r = sqrt(1 - sin^(2) r )= 0.8`
For CONSTRUCTIVE interference after reflection, `2 mu t cos r = (2n + 1) (lambda)/(2)`
Solving `t = 0.14 (2n + 1)mu m`.


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