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Optics BLOCK 4 > Polarization II > Flashcards

Polarization II Flashcards

1
Q

The blue light is __________ for light coming from the points in the sky 90 degrees away from the sun

A

Linearly polarized (rayleigh)

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2
Q

The light coming from directions near the sun or opposite the sun is _________

A

Unpolarized (Mie)

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3
Q

For regions in between 90 away from the sun and around the sun, the light is ________

A

Partially polarized (tyndall)

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4
Q

Waggle dance of the bee shows not only the ________ of he food, but also the __________ of the food location

A

Direction

Distance

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5
Q

What is the purpose of the tail waggling dance of a bee?

A

To communicate the direction of food to the other bees relative to the position of the sun

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6
Q

What is a requirement for a correct waggle dance for a bee

A

Must be able to read the suns postion from the blue sky.

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7
Q

Photoreceptors of the bees compound eyes

A

Exhibit a strong sensitivity to polarized light

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8
Q

Bees have a ___________ in the medulla, suggesting that polarization patterns in the sky may be analyzed by the brain

A

Polarization sensitive neuron

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9
Q

When one views objects through a properly oriented transparent, polished calcite crystal, the image is doubled. This phenomenon is known as __________________

A

-birefringence or double refraction

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10
Q

The light associated with each image is ________________ to that of the other ( in birefringence)

A

Plane-polarized perpendicular

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11
Q

The material of a birefringent object

A

Has different structure in different directions (anisotropic)

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12
Q

For incident frequency, crystal (anisotropic medium) is _________ for both the horizontally and vertically polarized light

A

Transparent

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13
Q

The ______________ are different for the two polarizations. This difference in refractive index leads to the birefringence or double refraction phenomenon

A

Refractive indices

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14
Q

When light propagates down the internal optical axis crystal, the different polarization components travel at ______________ due to the different indices of refraction

A

Different speeds

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15
Q

What happens when a light passes through a refractive index?

A
  • wavelength changes
  • speed changes
  • frequency does not
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16
Q

What remains constant when light passes through a refractive index?

A

Frequency

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17
Q

The polarization component perpendicular to the plane of the paper behaves as expected and the associated ray is called the _________

A

Ordinary or o-ray

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18
Q

The polarization component represented by the double arrows does not behave as expected, instead it moves diagonally upward as it propagates through the crystal. The ray associated with this component is labeled ______

A

The extraordinary or e-ray

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19
Q

A crystal that transmits one component and absorbs the other

A

Dichrotic

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20
Q

The property by certain materials having different absorption coefficients for light polarized in different directions

A

Dichroism

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21
Q

What is intrinsic dichroism based on?

A

Specific absorption properties of the materials

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22
Q

What is form dichroism based on?

A

Specific structure of the materials (calcide crystal)

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23
Q

Birefringence is introduced by ________ of a material

A

Anisotropy

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24
Q

What does the anisotropy of a material depend on?

A

The refractive index of the material depends on the direction of light propagation and on the polarization state of the light

25
Q

Birefringence in biological tissue

A

Anisotropy is often generated by a compounding of at least two homogenous dielectric materials

26
Q

How do you observe measurable birefringence in biological material

A

Materials have to be arranged in an organized manner

Fibrils that are surrounded by material of different refractive index

27
Q

Birefringence of a organized manner is called

A

Form birefringence

28
Q

When light traverses a birefringent materials, a relative delay between two orthogonal polarization states is introduced that accumulates with thickness of the material. This delay is known as

A

Phase retardation

29
Q

Creates 90 degree phase shift. Converts linear polarization into circular polarization

A

Quarter wave plate

30
Q

Difference in optical path length

A

(N slow-n fast)d = optical path difference

This is what produces birefringence

31
Q

Rotates a linear polarization by 90

A

Half wave plate

32
Q

Very small changes in refractive index can do what to polarization

A

Create very large changes in polarization that can be easily visualized with a polariscope

33
Q

In the normal eye, polarization specific retardation of light occurs mainly in the ________, which contributes about _______ of the birefringence of the eye

A

Cornea

80%

34
Q

Where does the remaining birefringence of the eye after the cornea originate from?

A

Retinal nerve fiber layers and Henle fibers of the central macula

35
Q

The crystalline lens, tear film, aqueous humor and vitreous and birefringence

A

Insignificant amount to the total ocular birefringence

36
Q

Due to birefringence of cornea and lens, the state of polarization changes from linear to ___________

A

Elliptical

37
Q

What causes more retardation partial polarization in the eye

A

Scattering of the fundus

38
Q

Reflected polarized light in the eye

A

Affected again on this way back before exiting the eye

39
Q

Birefringent property of cornea are due to its special structure ____________ called ‘stroma’

A

Form birefringence

40
Q

How much of the cornea does the stroma make up?

A

9/10 of the thickness of the cornea

41
Q

Retardation in the cornea will increase with what?

A

Angle of incidence

42
Q

If light is incident parallel to the surface of the cornea, there is no _______

A

Retardation

43
Q

When light hits the cornea at an eccentric angle of incidence this will cause _________

A

Retardation

44
Q

What surface of the cornea is birefringence greater?

A

Anterior surface

45
Q

What could alter the corneal birefringence

A
  • IOP
  • higher astigmatism
  • corneal asymmetry
  • post op corneal distortion
46
Q

What does the maltese cross appearance come from in the cornea

A

Results from the regular arrangement of collagen lamellar in the cornea, which are birefringent

47
Q

What is the birefringent property of the crystalline lens due to?

A

Form birefringence

48
Q

Total birefringence of the lens

A

Negligible compared to in cornea by a factor of 10

49
Q

Exhibits from birefringence due to the radially arranged nerve fiber layer of henle

A

Haidenger’s brush

50
Q

Why does the birefringent nerve fibers of the macula act like a yellow radial polarizing filter

A

Fiber layer of henle which lies over the rods and cones of the macular region

51
Q

Haidenger’s brush apparatus

A

Consists of a blue filter and a rotating linear polaroid placed over a light bulb

52
Q

What is the haidenger’s brush apparatus used for?

A

Used to detect, diagnose, and train amblyopia due to eccentric fixation

53
Q

Disruption or absence of a bow tie on the macula in fundus photo

A

Indicate severe damage to the photoreceptors, consistent with the finding of poorer visual acuity

54
Q

When could patients perceive haidenger’s brushes?

A

When the proportion of polarized light reached 56 percent, although some could see them in only 25 percent polarized light

55
Q

An ability to measure and test a persons ability to perceive polarization could potentially offer what

A

A simple and affordable screen for AMD

56
Q

The study of how humans perceive polarization showed that your ______ can dramatically affect how you perceive polarized light

A

Cornea

57
Q

Tool used to qualitatively assess birefringence of a material

A

Polariscope

58
Q

The poalriscope is used to _______________

A

Assess birefringence in materials

59
Q

Visualization of birefringence using a polariscope provides information about

A
  1. Lens material and how processed
  2. Stress on the lens
  3. The likely locations at which line fractures may occur if the lens is dropped or bumped

Localized birefringence indicates a weak point in the lens, which if significant should be replaced

Optics BLOCK 4 (15 decks)

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