QJEEM14Pha1e5: JEE Main 2014 Physics - Class 12 JEEM14Pha1e5 Solution: Two beams, and , of plane polarized light with mutually…

Question

Verified Solution • 2025–26 Session moderate

Two beams,

A

and

B

, of plane polarized light with mutually perpendicular planes of polarization are seen through a polaroid. From the position when the beam

A

has maximum intensity (and beam

B

has zero intensity), a rotation of polaroid through

{30^ \circ }

makes the two beams appear equally bright. If the initial intensities of the two beams are

{{\rm I}_A}

and

{{\rm I}_B}

respectively, then

{{{{\rm I}_A}} \over {{{\rm I}_B}}}

equals:

Accepted Answer

According to malus law, intensity of emerging beam is given by,

I = {I_0}{\cos ^2}\theta

Now,

{I_{A'}} = {I_A}{\cos ^2}{30^ \circ }

{I_{B'}} = {I_B}{\cos ^2}{60^ \circ }

As

{I_{A'}} = {I_{B'}}

\Rightarrow {I_A} \times {3 \over 4} = {I_B} \times {1 \over 4}

\therefore

{{{I_A}} \over {{I_B}}} = {1 \over 3}

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