Scattering Flashcards by Sade Kehinde

Q

Scattering of light is caused due to the in-homogeneities in a medium
in-homogeneities = _______

A

particles

How well did you know this?

1

Not at all

2

3

4

5

Perfectly

Q

Two MAIN types of scattering

A

Incoherent

Coherent

How well did you know this?

1

Not at all

2

3

4

5

Perfectly

Q

CONDITIONS for Incoherent Scattering:
1
2

A

white light

particles far apart

How well did you know this?

1

Not at all

2

3

4

5

Perfectly

Q

Incoherent scattering depends on :

A

size of particles

distance btw particles

strenght of interaction:- refractive index
absorption strength

How well did you know this?

1

Not at all

2

3

4

5

Perfectly

Q

Mie scattering, Tyndale scattering, or Rayleigh scattering?

particle size > wavelength of light

A

M

How well did you know this?

1

Not at all

2

3

4

5

Perfectly

Q

Mie scattering, Tyndale scattering, or Rayleigh scattering?

particle size = wavelength of light

A

T

How well did you know this?

1

Not at all

2

3

4

5

Perfectly

Q

Mie scattering, Tyndale scattering, or Rayleigh scattering?

particle size < wavelength of light

A

R

How well did you know this?

1

Not at all

2

3

4

5

Perfectly

Q

Mie scattering, Tyndale scattering, or Rayleigh scattering?

• reflection & refraction
causes scattering

A

M

How well did you know this?

1

Not at all

2

3

4

5

Perfectly

Q

Mie scattering, Tyndale scattering, or Rayleigh scattering?

Example: halos seen through
a fogged up car window

A

T

How well did you know this?

1

Not at all

2

3

4

5

Perfectly

Q

Mie scattering, Tyndale scattering, or Rayleigh scattering?

• forward direction scattering

A

M

How well did you know this?

1

Not at all

2

3

4

5

Perfectly

Q

Mie scattering, Tyndale scattering, or Rayleigh scattering?

dipole re-radiation causes
scattering

A

R

How well did you know this?

1

Not at all

2

3

4

5

Perfectly

Q

Mie scattering, Tyndale scattering, or Rayleigh scattering?

stronger dependence at
shorter wavelength (blue)
than on the longer
wavelength

A

R

How well did you know this?

1

Not at all

2

3

4

5

Perfectly

Q

Mie scattering, Tyndale scattering, or Rayleigh scattering?

spread light out in more
direction

A

T

How well did you know this?

1

Not at all

2

3

4

5

Perfectly

Q

Mie scattering, Tyndale scattering, or Rayleigh scattering?

wavelength independent

A

M

How well did you know this?

1

Not at all

2

3

4

5

Perfectly

Q

Mie scattering, Tyndale scattering, or Rayleigh scattering?

• interior wave effects causes
scattering (diffraction)

A

T

How well did you know this?

1

Not at all

2

3

4

5

Perfectly

Q

Mie scattering, Tyndale scattering, or Rayleigh scattering?

Examples: Blueness of the sky

A

R

How well did you know this?

1

Not at all

2

3

4

5

Perfectly

Q

Mie scattering, Tyndale scattering, or Rayleigh scattering?

wavelength dependent

A

T

How well did you know this?

1

Not at all

2

3

4

5

Perfectly

Q

Mie scattering, Tyndale scattering, or Rayleigh scattering?

Example: whiteness of the
clouds

A

M

How well did you know this?

1

Not at all

2

3

4

5

Perfectly

Q

Mie scattering, Tyndale scattering, or Rayleigh scattering?

isotropic in direction (all)
scattering profile shows forward and backward scatter

A

R

How well did you know this?

1

Not at all

2

3

4

5

Perfectly

Q

_________Scattering is an elastic scattering,
as the scattered photons’ energy do not
change

A

Rayleigh

How well did you know this?

1

Not at all

2

3

4

5

Perfectly

Q

Inelastic scattering of particles is called

______ Scattering.

A

Raman

How well did you know this?

1

Not at all

2

3

4

5

Perfectly

Q

________ Scattering theory applies for particles both absorb and scatter.

A

Mie

How well did you know this?

1

Not at all

2

3

4

5

Perfectly

Q

Techniques based on scattering theory are used in several studies in the understanding of optical
properties of biological tissues like skin, brain, breast, bone, other soft tissues, other fibrous tissues and
fatty tissues, and even blood cell

A

Mie

How well did you know this?

1

Not at all

2

3

4

5

Perfectly

Q

The bluer the light the more the light_______
and the larger the area of
________

A

scatters

glare

How well did you know this?

1

Not at all

2

3

4

5

Perfectly

Mie scattering produces ______ scattered light

unpolarized

Rayleigh : when reflected and transmitted light are perpendicular , get strong _________

polarization

In 1882, _________published Le Rayon Verte – the Green Ray – in which he dreamed up an old Scottish legend that says anyone who sees a green flash will never again make a misstep in matters of the heart.

Jules Verne

Coherent scattering: When the particles are ___________ than the coherence length of the light, ________and _______interference occurs between the waves scattered from different particles

much closer together constructive and destructive

Coherent scattering: Particles much_____ than the wavelength of the light • Each particles acts as a ________ for the coherent scattered waves • Scattered waves propagate ______ and overlap. • Acts as ‘diffraction ______

smaller source outward grating

Many coherent scattered waves interfere… ______ in most directions •________ in two directions • _____to incident light (forwardscatter) • Refract _______ to incident wave (phase shifted)

• Destructively Constructively Parallel relative

``` Intraocular Light scatter: leads to deleterious visual effects, like • Glare while __________ • Hindrance from _______ during daytime • _______recognition problems • _______of vision • Color and contrast _____ ```

night driving low sun Facial Haziness loss

Light going into the | eye?

• Forward scatter (FWS) –

Light reflecting | back from the fundus?

• Backward scatter (BWS) – Light reflecting | back from the fundus

Small protein particles (α-crystallin) and rough surface reflectance dominate ________light scattering • Whereas, large sized protein particles dominate________ scattering.

backward forward

____________consists of Collagen Fibrils (parallel bundles) which are less than wavelength of the light. • Incomplete destructive interference causes about 10% scattering in cornea. • Corneal scattering helps in slit-lamp examination of the cornea.

Corneal stroma

The Collagen fibers (random order) in _____have larger spacing than the wavelength of light. • Due to large particle incoherent forward scattering, ________ appears whitish.

sclera | sclera

Case: ________ Fibers get smaller and sclera takes | on a bluish due to Rayleigh-type scattering.

Scleral thinning.

: • Yellow pigments in the lens scatter more light (forward scatter). • Cataract is formed when protein in the lens clumps together forming fluid pools causing additional scattering. • Cataract formation degrades vision by scattering. The amount of scatter increases with the cataract growth.

Crystalline lens

• With the coalescing of ‘collagen fibers’ in _______due to aging causes fluid packets and thereby developing a localized scattering. • This causes patients to see floating specks and threads.

Vitreous humor

________ scatters light as much as cornea. • When blood circulation/supply is interrupted, the ______ integrity is damaged, and edema fluid starts collecting in the nerve fiber layer. This increases______light scattering turning the area into milky gray (cotton wool spots).

retina retinal retinal

Sources of Ocular scattering: | 5:

Sources of Ocular scattering: 1. Cornea 2. Sclera and Iris 3. Lens 4. Vitreous humor 5. Retina

``` __________ scattering is identical for all healthy eyes, and for all ages. (Constant)+ ```

Corneal light

__________ wearers experience a significantly higher light scatter.*

Contact lens

Corneal light scatter may increase after _____________

laser refractive surgery

surgery type? – Mean stray light increase by a factor of 1.4 in eyes with 4 mm pupil and a factor of 2 (0.3 log units) for 8mm pupil.

Radial Keratotomy (RK)*

surgery type? –corneal backscattering of light, which correlates with visible haze, is significantly stronger after _____ •

• Photorefractive keratotomy (PRK)*

surgery type?– Epithelial ingrowth after ________can cause an increase in straylight. •

Laser-assisted in situ keratomileusis (LASIK)*

surgery type? - Reported decreased | scatter in the follow ups.

Corneal Refractive Therapy (Orthokeratology or Corneal reshaping)*

The amount of scattering/stray light in the eye depends also on the pigmentation in the _________

fundus.

• Sclera and iris are not totally opaque.They diffusely transmit long wavelengths due to the________ in the scleral wall and iris.

color of the pigments

For a light-blue eye effective transmission of the iris was___%for red and ___% for green light. Also the eyewall around the iris transmits a significant amount of light.

1% | 0.2

Fundus has stronger reflectance of ____ wavelength ____ due to the pigments, and also the blood. • Blue eyes, blue-green eyes causes greater________ of light from fundus and more light transmission through the eye walls.

longer red back scattering

For the dark-brown eyes of pigmented individuals transmission is lower by____orders of magnitude.* Dark brown eye has abundant melanin pigments which absorbs strongest at ______ wavelength.#

two shorter

For natural pupils (between 2 and 7 mm diameter), scatter _______depends on pupil diameter

weakly

``` Light scatter by _____________ increases significantly with age and much more higher for cataract eyes ```

crystalline lens

___________ are the result of water absorption and subsequent phase separation within the IOL matrix and are clinically observed in almost all types of IOL material, including hydrophobic and hydrophilic acrylics, silicone, and PMMA.

Glistenings

: Radiation of sharp needles of light that is perceived subjectively around a bright point light source. • Originates from light scattering by small particles.

Ciliary Corona

• The ________ is a colored band, much like the rainbow, perceived surrounding a bright spot of light at a mean distance of 3° radius. • it originates from the fibrous structure of the eye lens. • the lens fibers form a diffraction grating, arranged in a circular fashion, much like the spokes of a wagon wheel. • the_______ appears only for______pupil sizes, depending on the subject

lenticular halo lenticular halo larger

: are introduced IOLs to reduce the amount of blue light transmission in the eye (Natural Chromophore).

blue light blocker*

blue light blocker benefits

``` Drastically reduces the light scatter (see below) • Blocks Blue light harmful to retina • Reduce the effect of chromatic aberrations of the eye. • Do not affect VA, CS, & Color vision ```

blue light blocker side effects

Potential side effects of a reduction in blue-light transmission include color-vision disturbance, decreased scotopic sensitivity (which can lead to poorer performance in dim lighting conditions), and sleep–wake timing disruption.