Intensity of Polarised Light

Q. Two beams, $A$ and $B$, of plane polarized light with mutually perpendicular planes of polarization are seen through a polaroid. From the position when 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 $I_A$ and $I_B$ respectively, then $\frac{I_B}{I_A}$ will be equal to

Q. A polarizer-analyzer set is adjusted such that the intensity of light coming out of the analyzer is just $10\%$ of the original intensity. Assuming that the polarizer-analyzer set does not absorb any light, the angle by which the analyser need to be rotated further to reduce the output intensity to be zero is

1. ${45}^o$
2. ${71.6}^o$
3. ${90}^o$
4. ${18.4}^0$

Q. Unpolarized light with an intensity of $I_0=16\frac{W}{m^2}$ is incident on a pair of polarizers. The first polarizer has its transmission axis aligned at ${50}^{\circ }$ from the vertical. The second polarizer has its transmission axis aligned at ${20}^{\circ }$ from the vertical.

What is the intensity of the light when it emerges from the second polarizer?

1. $4\frac{W}{m^2}$
2. $8{\cos }^2{20}^{\circ }\frac{W}{m^2}$
3. $6\frac{W}{m^2}$
4. $12\frac{W}{m^2}$

Q. Unpolarized light with an intensity of $I_0=16\frac{W}{m^2}$ is incident on a pair of polarizers. The first polarizer has its transmission axis aligned at ${50}^{\circ }$ from the vertical. The second polarizer has its transmission axis aligned at ${20}^{\circ }$ from the vertical.

What is the intensity of the light when it emerges from the first polarizer?

1. $16{\cos }^2{50}^{\circ }\frac{W}{m^2}$
2. $8\frac{W}{m^2}$
3. $12\frac{W}{m^2}$
4. $4\frac{W}{m^2}$

Q. Unpolarized light of intensity $32\frac{W}{m^2}$ passes through three polarizers such that the transmission axis of the last polarizer is crossed with that of the first. The intensity of final emerging light is $3\frac{W}{m^2}$ . The angle between the first two transmission axes of the polarizers is:

1. ${10}^{\circ }$
2. ${30}^{\circ }$
3. ${45}^{\circ }$
4. ${60}^{\circ }$

Q. Unpolarized light of intensity I passes through an ideal polariser A. Another identical polarizer $B$ is placed behind $A$. The intensity of light beyond B is found to be $\frac{I}{2}$. Now another identical polarizer $C$ is placed between A and B. The intensity beyond $B$ is now found to be $\frac{I}{8}$. The angle between polarizer $A$ and $C$ is :

1. $0^{\circ }$
2. $0^{\circ }$
3. ${45}^{\circ }$
4. ${60}^{\circ }$

Q. A beam of plane polarized light falls normally on a polarizer of cross sectional area $3\times {10}^{–4}{\text{m}}^2$. Flux of energy of incident ray is ${10}^{–3}$ Watt. The polarizer rotates with an angular frequency of $31.4{\text{rad s}}^{–1}$. The energy of light passing through the polarizer per revolution will be -

1. ${10}^{-4}\text{Joule}$
2. ${10}^{-3}\text{Joule}$
3. ${10}^{-2}\text{Joule}$
4. ${10}^{-1}\text{Joule}$

Q. How does the intensity of transmitted light depend upon the angle between $\ast$ the polariser and analyser? Show it graphically

Q. A plane polarized light is incident normally on the tourmaline plate. Its $\overrightarrow{E}$ vectors, make an angle of ${60}^o$ with the optic axis of the plate. Find the $\%$ difference between initial and final maximum values of $\overrightarrow{E}$ vectors.

Q. On unpolarised beam of light is incident on a set of four polarising plates, such that each plate makes an angle of $\frac{\pi }{3}$ with preceding sheet. The light transmitted through the combination is:-

1. $\frac{1}{128}$
2. $\frac{1}{256}$
3. $\frac{1}{64}$
4. $\frac{1}{32}$