Saved Bookmarks
| 1. |
Two polaroids are kept corssed ("transmission axesat " 90^(@)) to each other. (i) What will be the intensity of the light coming out from the seond polaroid when an unpolarised light of intensity I falls on the first polaroid? (ii) What will be the intensity of light coming out from the second polaroid if a thrid polaroid is kept at 45^(@) inclination to both of them. |
|
Answer» Solution :(i) As the intensity of TH umpolarised light FALLING on the first polaroid is I, theintensity of POLARIZED light emergingfrom it will be `I_(0)=((1)/(2)).` Let I. be the intensity of light emerging from the SECOND polaroid. Malus. law, `I. = I_(0) cos^(2) theta` Here `theta is 90^(@)` as the transmission axes are perpendicular to eachother. Substituting. `1.=((1)/(2))cos^(2)(90^(@))=0"" [thereforecos(90^(@))=0]` No light comes out from the second polaroid. (II) Let the first polaroid be` P_(1)` and the second polaroid `P_(2)`. They are oriental at `90^(@)`. The third polaroid `P_(1)` introduced between them `45^(@)`. Let I. be the intensity of light emerging from `P-(3)`. Angle between `P_(1) and P_(3) is45^(@)`. The intensity of light coming out from `P_(3)is I. = I_(0) cos^(2) theta` Substituting, `I.=((1)/(2))cos^(2)(45^(@))=((1)/(2))((1)/(sqrt(2)))^(2)=(1)/(4):I.(1)/(4)` Angle betweem `P_(3) and P_(2) is45^(@)` . Let I. is the intensityof light coming ut coming `P_(2) I. = I.cos^(2) theta`.  Here, the intensity of polarized light existing between `P_(3)` and `P_(2) " is"(1)/(4)`. Substituting, `1^(n)=((1)/(4))cos^(2)(45^(@))=((1)/(4))((1)/(sqrt(2)))^(2)=(1)/(8)` `1^(n) = (1)/(8)` |
|