Polarisation, Brewster's law and Polaroids — practice questions

Question 1 · difficulty L1 · recall

Polarisation demonstrates that light is

• A. transverse
• B. longitudinal only
• C. a scalar with no field direction
• D. unable to interfere

Question 2 · difficulty L1 · understanding

Unpolarised light passing through an ideal polariser emerges

• A. unpolarised with identical directional distribution
• B. plane-polarised
• C. longitudinal
• D. with zero intensity always

Question 3 · difficulty L2 · understanding

An unpolarized light of intensity $I_0$ passes through polarizer and then through a certain optically active solution and finally it goes to analyser. If the angle between analyser and polariser is $0^{\circ}$ and intensity of light emerged from analyser is $\frac{3}{8} I_0$, the angle of rotation of the light by the solution with respect to analyser is $\_\_\_\_$ degrees.

Question 4 · difficulty L2 · understanding

As shown in the figure, three identical polaroids P$$_1$$, P$$_2$$ and P$$_3$$ are placed one after another. The pass axis of P$$_2$$ and P$$_3$$ are inclined at angle of 60$$^\circ$$ and 90$$^\circ$$ with respect to axis of P$$_1$$. The source S has an intensity of 256 $$\frac{W}{m^2}$$. The intensity of light at point O is ____________ $$\frac{W}{m^2}$$.

Question 5 · difficulty L2 · understanding

An unpolarised light beam is incident on the polarizer of a polarization experiment and the intensity of light beam emerging from the analyzer is measured as 100 Lumens. Now, if the analyzer is rotated around the horizontal axis (direction of light) by 30$$^\circ$$ in clockwise direction, the intensity of emerging light will be _________ Lumens.

Question 6 · difficulty L2 · understanding

As shown in the figure, a ray AB of unpolarized light enters from water of refractive index $n_w = \frac{4}{3}$ into a medium of refractive index $n_p = \frac{4}{\sqrt{3}}$ after passing through a glass plate of refractive index $n_g = 1.5$ and a layer of water. At a particular incident angle $i$ the reflected ray CD is polarized in the direction as shown in the figure. The value of $i$ (in degrees) is :

Question 7 · difficulty L2 · understanding

When an unpolarized light falls at a particular angle on a glass plate (placed in air), it is observed that the reflected beam is linearly polarized. The angle of refracted beam with respect to the normal is $\_\_\_\_$ . $\left(\tan ^{-1}(1.52)=57.7^{\circ}\right.$, refractive indices of air and glass are 1.00 and 1.52, respectively.)

• A. $36.3^{\circ}$
• B. $39.6^{\circ}$
• C. $42.6^{\circ}$
• D. $32.3^{\circ}$

Question 8 · difficulty L2 · understanding

Two plane polarized light waves combine at a certain point whose electric field components are $$\begin{aligned} & E_1=E_0 \operatorname{Sin} \omega t \\ & E_2=E_0 \operatorname{Sin}\left(\omega t+\frac{\pi}{3}\right) \end{aligned}$$ Find the amplitude of the resultant wave.

• A. $1.7 \mathrm{~E}_0$
• B. $\mathrm{E}_0$
• C. $0.9 \mathrm{~E}_0$
• D. $3.4 \mathrm{~E}_0$

Question 9 · difficulty L2 · understanding

When unpolarized light is incident at an angle of $$60^{\circ}$$ on a transparent medium from air, the reflected ray is completely polarized. The angle of refraction in the medium is:

• A. $$60^{\circ}$$
• B. $$90^{\circ}$$
• C. $$30^{\circ}$$
• D. $$45^{\circ}$$

Question 10 · difficulty L2 · understanding

A beam of unpolarised light of intensity $$I_0$$ is passed through a polaroid $$A$$ and then through another polaroid $$B$$ which is oriented so that its principal plane makes an angle of $$45^{\circ}$$ relative to that of $$A$$. The intensity of emergent light is:

• A. $$I_0 / 2$$
• B. $$I_0 / 8$$
• C. $$I_0 / 4$$
• D. $$I_0$$