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Optics > Diffraction 1 (10-11) > Flashcards

Diffraction 1 (10-11) Flashcards

1
Q

A diffraction grating made of _______slits

A

‘circular

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2
Q

• An optical device that blocks alternate zones is called

a

A

‘Zone Plate’

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3
Q

A diffraction grating that creates inwardly bending

‘spherical’ diffracted wave forms a ._______

A

‘point image’

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4
Q

For a ___________source of light incident on a zone plate:
• Central order (0th) goes through
• First order (1st) forms point image at___
.
• Second order forms point image at ____
• Third order forms point image at _____

A

monochromatic

straight.

f2

f2/2.

f2/3

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5
Q

___________ blocks wave that contribute to
destructive interference at the diffraction maximum,
making the image formation much__________

A

Fresnel zone plate

‘dimmer’.

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6
Q

Phase Plate:

Instead of blocking these waves, they are phase shifted
by _______

Then, the phase shifted waves would be________with the axial wave, and would contribute to the
_________ interference at the diffraction maximum,
making the image much________

A

180°.

in phase

constructive

‘brighter’.

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7
Q

Ways to make ‘Phase Plate’ by adjusting -

  1. No. of _______
  2. Depth of the____ d)
  3. Refractive ______μ)
  4. __________
A

grooves

groove (

Index (

Wavelength(λ)

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8
Q

A zone plate with kinoform shaped grooves

is referred to as a _______

A

diffractive lens.

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9
Q

: A single
refractive lens with a
phase plate imbedded on
one side of its surfaces.

A

Hybrid lens

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10
Q

A Fresnel lens with equal zone widths. A Fresnel

lens is always a ______lens.

A

mono-focal

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11
Q

Diffractive Lens Design Details:

Local grating ______determines ray direction (add power).

Spacing gets progressively smaller from____ to its
______.

A

spacing

center to its edge.

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12
Q

Diffractive Lens Design Details:

Local Step______determines ‘diffraction efficiency’ of light.
[determines how much light put into the add portion]

A

height

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13
Q

Allocation of energy into each diffraction order
When m= ____focal length of 0th order is infinite (zero
power).
The base power of the lens provides all the power at
this order. At this power, ______ vision is corrected.
When m=_____ energy is distributed to the 1
st order.

A

=0,
distant
=1,

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14
Q

Unwanted patterns onto the retina
which affect the visual performance by
obscuring relevant retinal image.

A

Dysphotopsia

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15
Q

Bright artifacts onto the retina.

Ex. Arcs, rings, streaks, halos & glare

A

Positive Dysphotopsia:

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16
Q

Blockage of light onto the retina.

Ex. Shadows, dark spots.

A

Negative Dysphotopsia:

17
Q

Fresnel’s lens increases the luminosity of the

lighthouse lamp by a factor of ______

A

4.

18
Q 
\_\_\_\_\_\_\_\_Lighhouse in Waimanalu,
Hawaii. The lighthouse
has a hyper-radiant
Fresnel lens with a 1.3-m
focal length, one of the
largest in the world.
A

Makapuu

19
Q

Delivers color by absorption at
certain wavelength and reflects at
others)

A

chemistry

and pigment coloration

20
Q

Delivers color due to Interference,

diffraction & Scattering.

A

physics and structural patteren

21
Q

A component found on the insect

exoskeletons. RI, n = 1.53 – 1.56.

A

chitin

22
Q

_______________causes ‘iridescence’ color.

A

Overlap of several orders of diffraction

23
Q

• Strength of the Iridescence depends on the__________ and ___________

A

‘groove density’ and

the ‘surface quality’.

24
Q

0th order is very _____

3rd-8th order is ______

A

intense

iridescence

25
Q

Holography:
Developed by__________ in 1948. Had to wait until the invention of Lasers (Coherent source) to record a hologram. In _______received Noble prize in physics

A

Dennis Gabor

1971

26
Q

Requirements of Holography :
_______ Light
Maintain ‘_______ of 2 waves
constant all through out

Extremely complicated ______________

A

Coherent

phase relationship’

Interference

27
Q

Unlike conventional imaging, in_________imaging ‘Light from each point on the object will reach all points on the film’

A

holographic

28
Q

holography: _________causes Interference pattern to
be formed producing an image with 3D
information.

A

Phase-difference

29
Q

Requires a_________Source to view the holographic image recording

A

Coherent

30
Q

__________ in 1969 invented ‘rainbow’ hologram

– a second generation holography.

A

Stephen Benton

31
Q

________ viewed – You will see ‘3D image’
_________viewed – You will see ‘different colors’
Types of Holograms: ____________

Real Image formed (m=+1) are not normal viewed

Virtual Image formed (m=-1) behind the film are viewed

A

Horizontally

Vertically

Transmission and Reflection

32
Q

For the eye, only a section passes through the pupil; the iris is an obstruction that diffracts the light. This
diffraction blurs the image. For a system limited only by diffraction (no optical aberrations), the image radius for a
point object =__________

A

1.22 λ f/d meters.

33
Q

Pupil size controls impact of ___________ and ___________on retinal image quality (emmetrope)

A

ocular aberrations

diffraction

34
Q

collagen:

A fibril spacing (d) ______than the wavelength of light (λ) will make
the fibrils transparent as light passes through undeviated.

A

smaller

35
Q

If d < λ then θ > 90 deg for all m > 0.
Therefore, no diffraction orders exist except _____
Under this condition, the fibrils diffract no light
and appear transparent.

A

m = 0.

36
Q

WHAT IS THIS TALKING ABOUT?
Light entering the eye is diffracted by small
particles in the eye.
Each particle causes a circular diffraction
pattern on the retina tens of degrees across.
Interference of overlapping diffraction
patterns for white light is easily observed by
viewing a small, bright, white light source.
We perceive a very fine pattern of
innumerable needles of light, fanning out
from the point object over several degrees.

A

The

ciliary corona

is an entoptic diffraction phenomeno

Optics (5 decks)

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