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The polaroids P_(1) and P_(2) are placed in crossed position. A third polaroid P_(3) is kept between P_(1) and P_(2) such that pass axis of P_(3) is parallel to that of P_(1). How would the intensity of light (I_(2)) transmitted through P_(2) vary as P_(3) is rotated ? Draw plot of intensity I_(2) versus angle theta between pass axis of P_(1) and P_(3). In which orientation will the transmitted intensity be minimum and maximum ? |
Answer»  If `THETA` is angle between `P_(1) and P_(3)`, the angle between `P_(3) and P_(2) = (90 - theta)` By Law of Malus, `I_(3) = I_(1) cos^(2) theta` and `I_(2) = I_(3) cos^(2)(90 - theta) = I_(3) sin^(2)theta` `= I_(1) cos^(2) theta sin^(2)theta = (1)/(4)I_(1)(2 sin theta cos theta)^(2)` `I_(2) = (1)/(4) I_(1) sin^(2) 2theta` The plot of `I_(2)` versus `theta` is as shown in Fig.  TRANSMITTED intensity `I_(2)` will be minimum. When `sin 2 theta = 0 or theta = 0^(@)`. Transmitted intensity will be maximum, when `sin 2 theta = 1, 2 theta = 90^(@), theta = 45^(@)` |
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