Intensity of Polarised Light

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. 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. Two sources $S_1$ and $S_2$ emitting light of wavelengths $600\text{nm}$ are placed a distance $1\times {10}^{-2}\text{cm}$ apart. A detector can be moved on the line $S_{1}P$ which is perpendicular to $S_1{S}_2$. Find out the position of the first minimum detected.

1. $1.7\text{cm}$
2. $8.12\text{cm}$
3. $4.2\text{cm}$
4. $2.5\text{cm}$

Q. Intensity of unpolarised light incident on a polarizer is $2a^2$ then amplitude of emergent ray (Assuming zero absorption in the Polaroid)

1. $\frac{a}{2}$
2. a
3. $\frac{\sqrt{3}a}{2}$
4. $\frac{3a}{4}$

Q. When the angle of incidence on a material is ${60}^{\circ }$, the reflected light is completely polarized. The velocity of the refracted ray inside the material is $\left({\text{in ms}}^{-1}\right)$

1. $0.5\times {10}^8$
   
2. $3\times {10}^8$
3. $\sqrt{3}\times {10}^8$
4. $\left(\frac{3}{\sqrt{2}}\right)\times {10}^8$

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. 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. ${10}^{-1}\text{Joule}$