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Two Nicol polarisers are oriented with their principal planes making an angle of 60º. The percentage of incident unpolarised light which passes through the system is

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Important Questions on Wave Optics

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Physics>Optics>Wave Optics>Polarisation

A polarizer - analyser set is adjusted such that the intensity of light coming out of the analyser is just

10 %

of the original intensity. Assuming that the polarizer - analyser set does not absorb any light, the angle by which the analyser needs to be rotated further, to reduce the output intensity to zero, is

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Physics>Optics>Wave Optics>Polarisation

Two Polaroids

P_{1}

and

P_{2}

are placed with their axis perpendicular to each other. Unpolarised light with intensity

I_{0}

is incident on

P_{1}

. A third polaroid

P_{3}

is kept in between

P_{1}

and

P_{2}

such that its axis makes an angle

45^{o}

with that of

P_{1}

. The intensity of transmitted light through

P_{2}

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Physics>Optics>Wave Optics>Polarisation

A system of three polarizers

P_{1}, P_{2}, P_{3}

is set up such that the pass axis of

P_{3}

is crossed with respect to that of

P_{1}

. The pass axis of

P_{2}

is inclined at

60^{o}

to the pass axis of

P_{3} .

When a beam of unpolarized light of intensity

I_{o}

is incident on

P_{1},

the intensity of light transmitted by the three polarizers is

I

. The ratio

(I_{o} / I)

equals (nearly):

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Physics>Optics>Wave Optics>Polarisation

The Brewsters angle

i_{b}

for an interface should be

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Physics>Optics>Wave Optics>Polarisation

Unpolarized light of intensity

I

is incident on a system of two polarizers,

A

followed by

B

. The intensity of emergent light is

\frac{I}{2}

. If a third the polarizer

C

is placed between

A

and

B

the intensity of emergent light is reduced to

\frac{I}{3}

. The angle between the polarizers

A

and

C

θ

, then

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Physics>Optics>Wave Optics>Polarisation

A beam of plane polarized light of large cross-sectional area and uniform intensity of

3 .3 W m^{- 2}

falls normally on a polarizer (cross-sectional area

3 \times 10^{- 4} m^{2}

), which rotates about its axis with an angular speed of

31 .4 rad s^{- 1}

. The energy of light passing through the polarizer per revolution, is close to:

EASY

Physics>Optics>Wave Optics>Polarisation

Unpolarized light of intensity

I

passes through an ideal polariser

A

. Another identical polariser

B

is placed behind

A

. The intensity of light beyond B is found to be

\frac{I}{2}

. Now another identical polariser

C

is placed between

A

and

B

. The intensity beyond B is now found to be

\frac{I}{8}

. The angle between polariser

A

and

C

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Physics>Optics>Wave Optics>Polarisation

Unpolarised red light is incident on the surface of a lake at incident angle $θ_{R}$ . An observer seeing the light reflected from the water surface through a polariser notices that on rotating the polariser, the intensity of light drops to zero at a certain orientation. The red light is replaced by unpolarised blue light. The observer sees the same effect with reflected blue light at incident angle $θ_{B}$ .

Then,

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Physics>Optics>Wave Optics>Polarisation

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 principle plane makes an angle of

45^{o}

relative to that of

A

. The intensity of the emergent light is:

EASY

Physics>Optics>Wave Optics>Polarisation

The polarising angle for transparent medium is

θ

v

is the speed of light in that medium. Then the relation between

θ

and

v

is (

c

= velocity of light in air)

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Physics>Optics>Wave Optics>Polarisation

Three polaroid sheets

P_{1}, P_{2}

and

P_{3}

are kept parallel to each other such that the angle between pass axes of

P_{1}

and

P_{2}

45 °

and that between

P_{2}

and

P_{3}

45 °

. If unpolarised beam of light of intensity

128 W m^{- 2}

is incident on

P_{1}

. What is the intensity of light coming out of

P_{3}

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Physics>Optics>Wave Optics>Polarisation

Unpolarized light of intensity

I_{0}

is incident on surface of a block of glass at Brewster's angle. In that case, which one of the following statements is true?

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Physics>Optics>Wave Optics>Polarisation

A ray of unpolarised light is incident on the glass surface of refractive index

1.73

at polarizing angle. The angle of refraction will be [Take

\tan 60 ° = 1.73

]

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Physics>Optics>Wave Optics>Polarisation

A transparent medium shows relation $i$ and $r$ as shown. If the speed of light in vacuum is $c,$ the Brewster angle for the medium is

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Physics>Optics>Wave Optics>Polarisation

A beam of light falls on a system of

4

polaroids, which are arranged in succession, such that the axis of each polaroids makes

30 °

with the axis of the preceding one. The fraction of the intensity of the incident light that passes through the system is

EASY

Physics>Optics>Wave Optics>Polarisation

When an unpolarized light of intensity

I_{0}

is incident on a polarizing sheet, the intensity of light which does not get transmitted is

EASY

Physics>Optics>Wave Optics>Polarisation

In a stạck of three polarising sheets, the first and the third are crossed while the middle one has its axis at

45 °

to the axes of the other two. The fraction of intensity of an incident unpolarised beam of light that is transmitted by the stack is

EASY

Physics>Optics>Wave Optics>Polarisation

When the angle of incidence on a transparent material is

60 °

, the reflected light is completely polarised. The velocity of refracted ray inside the material is

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Physics>Optics>Wave Optics>Polarisation

Two circular linear polarisers are placed coaxially. The transmission axis of the first polariser is

30 °

from the vertical while the second one is at

60 °

, both in the clockwise sense. If an unpolarised beam of light of intensity,

I = 20 W m^{- 2}

is incident on this pair of polarisers, then the intensities

I_{1}

and

I_{2}

transmitted by the first and the second polarisers, respectively, will be close to,

EASY

Physics>Optics>Wave Optics>Polarisation

Two beams, A and B of plane polarized light with mutually perpendicular planes of polarization are seen through a polaroid. From the position when the beam A has maximum intensity (and beam B has zero intensity), a rotation of polaroid through 30^o 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_{A}}{I_{B}}

equals :

Two Nicol polarisers are oriented with their principal planes making an angle of 60º. The percentage of incident unpolarised light which passes through the system is

Important Questions on Wave Optics

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