1.

Three indential polaroid sheets P_(1), P_(2) and P_(3) are oriented so that the pass axis of P_(2) and P_(3) are inclined at 60^(@) and 90^(@) resp. with respect to pass axis of P_(1). A monochromatic source of intensity I_(0) is Kept in front of the polaroid sheet P_(1). Find the intensity of this light as observed by O_(1), O_(2), O_(3) positioned as shown in Fig.

Answer»

Solution :When UNPOLARISED light PASSES through a polaroid, the intensity of transmitted light becomes half the intensity of unpolarised light.
`:.` Intensity of light observed by `O_(1)` is
`I_(1) = I_(0)//2`
(ii) Now, angle between `P_(1) and P_(2)` is `theta = 60^(@)`.
`:.` Intensity of light observed by `O_(2)` is
`I_(2) = I_(1) cos^(2) 60^(@) = (I_(0))/(2)((1)/(2))^(2) = (I_(0))/(8)`
(iii) Angle between `P_(2) and P_(3)` is ltbr. `theta = 90^(@) - 60^(@) = 30^(@)`.
`:.` Intensity of light observed by `O_(3)` is
`I_(3) = I_(2) cos^(2) 30^(@) = (I_(0))/(8)(SQRT(3)/(2))^(2) = (3 I_(0))/(32)`


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