A polaroid I is placed in front of a monochromatic source

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waveoptics

#1

A polaroid I is placed in front of a
monochromatic source. Another polaroid II is placed in front of this polaroid I and rotated till no light passes. A third polaroid III is now placed in between I and II. In this case, will light emerge from II. Explain.


#2

In the diagram shown, a monochromatic light is placed in front of polaroid (I) as shown below.

As, per the given question, monochromatic light emerging from polaroid I is plane polarised. When polaroid II is placed in front of this polaroid I and rotated till no light passes through polaroid II, then I and II are set in crossed positions, i.e. pass axes of I and II are at 90°.

When a polaroid III is placed in between I and II, no light will emerge from II, if pass axis of III is parallel to that of I or II. In all the other cases, light will emerge from II.