Brewster's Angle

Q. An unpolarised light is incident on a plate of refractive index $\sqrt{3}$ and the reflected light is found to be completely plane polarized. The angles of incidence and refraction are respectively

1. ${60}^{\circ },{30}^{\circ }$
   
2. ${30}^{\circ },{60}^{\circ }$
   
   
3. $si{n}^{-1}\left(\frac{1}{\sqrt{3}}\right),{45}^{\circ }$
   
   
4. $ta{n}^{-1}\left(\frac{\sqrt{3}}{2}\right),{30}^{\circ }$

Q. The velocity of light in air is $3\times {10}^8$ m/s and in a medium is $\sqrt{3}\times {10}^8$ m/s. The Brewster’s angle of the medium is

1. ${30}^{\circ }$
2. ${60}^{\circ }$
3. ${45}^{\circ }$
4. ${90}^{\circ }$

Q. 18. The path difference between two interfering wavesat a point on the screen is . The ratio of intensityat this point to the central bright fringe will be(Assume that intensity due to each slit is same)2(2) 4:3

Q. At what angle of incidence (in degrees) will the light reflected from water surface $(\mu =1.3)$ be completely polarized?(integers only)

Q. An unpolarised light is incident upon a glass plate of refractive index 1.54 at Brewster’s angle and gets completely plane polarized. The angle of polarization is: $(giventan{57}^{\circ }=1.54$)

1. ${57}^{\circ }$
2. ${46}^{\circ }$
3. ${33}^{\circ }$
4. ${82}^{\circ }$

Q. Whether all constant are dimensionless or unit less?

Q.

The angle between the incident ray and the reflected ray is $60°$. What is the value of the angle of incidence?

Q. The diagram shows four pairs of polarizing sheets, with the polarizing directions indicated by dashed lines. The two sheets of each pair are placed one behind the other, and the front sheet is illuminated by unpolarized light. The incident intensity is the same for all pairs of sheets. Rank the pairs according to the intensity of the transmitted light, least to greatest.

1. $1,2,3,4$
2. $4,2,1,3$
3. $2,4,3,1$
4. $2,1,4,3$

Q. When a light ray is incident at polarising angle on the surface
1) Reflected ray is completely polarised
2) Refracted ray is partially polarised
3) Intensity of refracted ray is less than incident ray

1. 1 is true
2. 2, 3 are true
3. 1, 2 are true
4. 1, 2, 3 are true

Q. A beam of light is falling on a glass plate at an angle ${60}^{\circ }$. It is found that the reflected light is completely polarized. The angle of refraction when angle of incidence is ${45}^{\circ }$ is

1. $si{n}^{-1}\left(\frac{1}{\sqrt{3}}\right)$
2. $si{n}^{-1}\left(\frac{\sqrt{3}}{2}\right)$
   
   
3. $si{n}^{-1}\left(\frac{1}{\sqrt{6}}\right)$
4. $si{n}^{-1}\left(\frac{1}{3}\right)$

Q. A light ray travels in two media A and B will speeds $2\times {10}^{8}m/s$ and $2.4\times {10}^{8}m/s$. The critical angle between them is

1. $si{n}^{-1}\left(\frac{8}{9}\right)$
2. $si{n}^{-1}\left(\frac{5}{6}\right)$
3. $ta{n}^{-1}\left(\frac{5}{6}\right)$
4. $co{s}^{-1}\left(\frac{8}{9}\right)$

Q.

Explain what is critical angle?

Q. A monochromatic light source of wavelength $\lambda$ is placed at $S$. Three slits $S_1,S_2$ and $S_3$ are equidistant from the source $S$ and the point $P$ on the screen $S_{1}P-S_{2}P=\frac{\lambda }{6}and{S}_{1}P-S_{3}P=\frac{2\lambda }{3}$.
If $I$ be the intensity at $P$ when only one slit is open, the intensity at $P$ when all the three slits are open is

1. $3I$
2. $5I$
3. $8I$
4. Zero

Q.

1. The optic axes of two Polaroids are inclined at an angle of 45° with each other.unpolarised light of intensity I° being incident on the first polaroid emerges from the second polaroid. What is the intensity of the emergent light?

Q.

A parallel beam of monochromatic light of wavelength $5000\stackrel{\circ }{A}$ is incident on a single narrow slit of width $0.001mm$. The light is focused by a convex lens on a screen placed on a focal plane. The first minimum will be formed for the angle of diffraction equal to

1. $50°$

2. $15°$

3. $20°$

4. $30°$

Q. What is the Brewster angle for air to glass transition? (Refractive index of glass = 1.5.)

Q. State the conditions based on Doppler effect

Q.

The intensity of light is inversely proportional to the square of distance from the source of light.

1. True
2. False

Q. State Brewster's law. Prove that if light is incident at the angle of polarization the reflected and refracted rays are mutually perpendicular.

Q. For what value of angle of incidence a ray incident on a glass plate $(\mu =1.5)$ will the reflected ray and the refracted ray be perpendicular to each other?

1. $\angle i={45}^{\circ }$
2. $\angle i={30}^{\circ }$
3. $\angle i={40}^{\circ }$
4. $\angle i={57}^{\circ }$

Q.

What is the value of the refractive index of the medium of Polarising angle${60}^{\circ }$?

Q. What happens when the source is not equidistant from the two slits

Q. The angle of incidence at which, reflected ray is totally polarised for reflection from air to glass (refractive index $=n$) is:

1. ${\sin }^{-1}\frac{1}{n}$
2. ${\sin }^{-1}n$
3. ${\tan }^{-1}\frac{1}{n}$
4. ${\tan }^{-1}n$

Q.

Two Polaroids P₁ and P₂ are placed with their axis perpendicular to each other. Unpolarised light I₀ is incident on P₁. A third polaroid P₃ is kept in between P₁ and P₂ such that its axis makes an angle 45⁰ with that P₁. The intensity of transmitted light through P₂ is:

1. $\frac{I_0}{16}$

2. $\frac{I_0}{2}$

3. $\frac{I_0}{4}$

4. $\frac{I_0}{8}$

Q.
A light beam of diameter 'd' is incident on a glass plate of refractive index $\frac{3}{2}$. If $\theta ={60}^{\circ }$ diameter of beam in glass becomes 'D', where $D=\left(a\sqrt{\frac{b}{c}}\right)d$ then $[\frac{c}{a}+b]$ is (a, b and c are integers less than 5. Write upto two digits after the decimal point.)

Q.

The figure represents a glass plate placed vertically on a horizontal table with a beam of unpolarised light falling on its surface at the polarising angle of $57°$ with the normal. The electric vector in the reflected light on screen S will vibrate with respect to the plane of incidence in a

1. vertical plane
2. horizontal plane
3. plane making an angle of $45°$ with the vertical
4. plane making an angle of $57°$ with the horizontal

Q. What is meant by polarisation angle? Find angle between reflected and refracted rays whenever light rays incident on polarisation angle. Draw suitable ray diagram.

Q. A ray of light is incident from a denser to a rarer medium. The critical angle for total internal reflection is ${\theta }_{iC}$ and the Brewster's angle of incidence is ${\theta }_{iB}$, such that $sin{\theta }_{iC}/sin{\theta }_{iB}=n=1.28$. The relative refractive index of the two media is :

1. 0.4
2. 0.9
3. 0.8
4. 0.2

Q. Polarising angle for water is ${53}^o{4}^{\prime }$. If light is incident at this angle on water and reflected, the angle of refraction is :

1. ${126}^o{56}^{\prime }$
2. ${36}^o{56}^{\prime }$
3. ${36}^o{20}^{\prime }$
4. ${30}^o$

Q. Unpolarized light is incident on a plane glass surface. The angle of incidence so that reflected and refracted rays are perpendicular to each other, then:

1. $tan{i}_{\beta }=\frac{\mu }{2}$
2. $tan{i}_{\beta }=\mu$
3. $sin{i}_{\beta }=\mu$
4. $cos{i}_{\beta }=\mu$