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(B) When two polaroids are crossed,the angle between their transmission axes is $	heta = 90^{\circ}$.When one polaroid is rotated by $45^{\circ}$,the

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$25$

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(B) When two polaroids are crossed,the angle between their transmission axes is $	heta = 90^{\circ}$.When one polaroid is rotated by $45^{\circ}$,the new angle between the transmission axes becomes $	heta' = 90^{\circ} - 45^{\circ} = 45^{\circ}$.According to Malus's Law,the intensity of light transmitted through the second polaroid is given by $I = I_{max} \cos^2(	heta')$,where $I_{max}$ is the intensity of light emerging from the first polaroid.Since unpolarized light of intensity $I_0$ is incident on the first polaroid,the intensity emerging from the first polaroid is $I_{max} = \frac{I_0}{2}$.Substituting the values,we get $I = \left(\frac{I_0}{2}ight) \cos^2(45^{\circ}) = \frac{I_0}{2} 	imes \left(\frac{1}{\sqrt{2}}ight)^2 = \frac{I_0}{2} 	imes \frac{1}{2} = \frac{I_0}{4}$.Therefore,the percentage of incident light transmitted is $\frac{I}{I_0} 	imes 100 = \frac{1}{4} 	imes 100 = 25\%$.

Two polaroids are kept crossed to each other. Now one of them is rotated through an angle $45^{\circ}$. The percentage of incident light now transmitted through the system is ......$\%$

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