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Flashcards in Polarization II Deck (59):
1

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

Linearly polarized (rayleigh)

2

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

Unpolarized (Mie)

3

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

Partially polarized (tyndall)

4

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

Direction
Distance

5

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

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

6

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

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

7

Photoreceptors of the bees compound eyes

Exhibit a strong sensitivity to polarized light

8

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

Polarization sensitive neuron

9

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

-birefringence or double refraction

10

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

Plane-polarized perpendicular

11

The material of a birefringent object

Has different structure in different directions (anisotropic)

12

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

Transparent

13

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

Refractive indices

14

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

Different speeds

15

What happens when a light passes through a refractive index?

-wavelength changes
-speed changes
-frequency does not

16

What remains constant when light passes through a refractive index?

Frequency

17

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

Ordinary or o-ray

18

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 ______

The extraordinary or e-ray

19

A crystal that transmits one component and absorbs the other

Dichrotic

20

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

Dichroism

21

What is intrinsic dichroism based on?

Specific absorption properties of the materials

22

What is form dichroism based on?

Specific structure of the materials (calcide crystal)

23

Birefringence is introduced by ________ of a material

Anisotropy

24

What does the anisotropy of a material depend on?

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

25

Birefringence in biological tissue

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

26

How do you observe measurable birefringence in biological material

Materials have to be arranged in an organized manner

Fibrils that are surrounded by material of different refractive index

27

Birefringence of a organized manner is called

Form birefringence

28

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

Phase retardation

29

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

Quarter wave plate

30

Difference in optical path length

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

This is what produces birefringence

31

Rotates a linear polarization by 90

Half wave plate

32

Very small changes in refractive index can do what to polarization

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

33

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

Cornea
80%

34

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

Retinal nerve fiber layers and Henle fibers of the central macula

35

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

Insignificant amount to the total ocular birefringence

36

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

Elliptical

37

What causes more retardation partial polarization in the eye

Scattering of the fundus

38

Reflected polarized light in the eye

Affected again on this way back before exiting the eye

39

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

Form birefringence

40

How much of the cornea does the stroma make up?

9/10 of the thickness of the cornea

41

Retardation in the cornea will increase with what?

Angle of incidence

42

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

Retardation

43

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

Retardation

44

What surface of the cornea is birefringence greater?

Anterior surface

45

What could alter the corneal birefringence

-IOP
-higher astigmatism
-corneal asymmetry
-post op corneal distortion

46

What does the maltese cross appearance come from in the cornea

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

47

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

Form birefringence

48

Total birefringence of the lens

Negligible compared to in cornea by a factor of 10

49

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

Haidenger's brush

50

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

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

51

Haidenger's brush apparatus

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

52

What is the haidenger's brush apparatus used for?

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

53

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

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

54

When could patients perceive haidenger's brushes?

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

55

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

A simple and affordable screen for AMD

56

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

Cornea

57

Tool used to qualitatively assess birefringence of a material

Polariscope

58

The poalriscope is used to _______________

Assess birefringence in materials

59

Visualization of birefringence using a polariscope provides information about

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