Optics Definitions

Question 1

What is diffraction?

Answer 1

Change in direction of propagation of light NOT DUE TO REFLECTION OR REFRACTION

Question 2

What is the phenomenon of diffraction

Answer 2

Deviation from rectilinear propagation that occurs when light advances beyond an obstruction

Question 3

If rays travel in straight lines, what should the shadow pattern look like?

Answer 3

Should have sharp edges!

-diffraction blurs the edges

Question 4

what is Huygens principle?

Answer 4

all points on a wavefront can be considered as point sources for the production of secondary wavelets

Question 5

Fresnel expanded Huygens principle to say…

Answer 5

-the secondary wavelets undergo MUTUAL INTERFERENCE

Question 6

for single-slit diffraction, how must d and wavelength be in relation to the width of the slit (a)?

Answer 6

• wavelegth must be greater than or equal to a

- d must be GREATER than a

Question 7

the angular location for the first minimum does what as the slit width increases?

Answer 7

-gets smaller!

Question 8

what is fresnel diffraction?

Answer 8

• near field

- source of light and the screen are at a finite distance from the diffraction aperature

Question 9

what is fraunhofer diffraction?

Answer 9

• far field

- source of light and the screen are at infinite distance from the diffraction aperature

Question 10

which diffraction, fresnel or fraunhofer, results in collimated light?

Answer 10

-fraunhofer (far)

Question 11

which diffraction is easy to observe and calculate?

Answer 11

fraunhofer (far)

Question 12

which diffraction can vary due to distance changes between the slit and the screen?

Answer 12

fresnel (near)

Question 13

what is a poisson spot?

Answer 13

bright in the center of a shadow

-present in Fresnel diffraction

Question 14

what is Rayleigh’s criterion?

Answer 14

-when the central maximum of one image falls on the first minimum of another image, the images are said to be JUST RESOLVED

Question 15

snellens acuity is equal to…

Answer 15

the reciprocal of the minimum resolvable angular detail

Question 16

If you already see 20/20 and look through a pinhole, what will happen to the VA?

Answer 16

-it will reduce to 20/30

Question 17

according to ISO standard, what resolution efficiency is acceptable for product release?

Answer 17

greater than or equal to 60%

Question 18

what is apodization?

Answer 18

remove the rings around the central maximum and concentrate energy in the central maximum

Question 19

what kind of filter eliminates diffraction pattern?

Answer 19

gaussian filter

Question 20

what is the stile crawford effect?

Answer 20

-light efficiency of of rays entering at the center of the pupil is greater than the rays entering through the edges

Question 21

diffraction grating consists of what?

Answer 21

-many slits with a very small slit separations

Question 22

what is blazed grating?

Answer 22

diffraction grating that is designed to channel light away from the central max into first or second order max

Question 23

what is the blazing angle?

Answer 23

angle at which efficiency is max

Question 24

diffraction grating efficiency reduces whith what?

Answer 24

reduces with higher wavelength

Question 25

how do you determine the nummber of seconday maxima of diffraction grating?

Answer 25

number of slits-2

Question 26

what is an Airy disk>

Answer 26

- diffraction pattern - bright center - airy pattern are the rings

Question 27

what is a zone plate?

Answer 27

-optical device that blocks alternate zones

Question 28

what is a point image?

Answer 28

-formed when a diffraction grating creates inwardly bending spherical diffraction wave

Question 29

zone plates block the wave that cotributes to destructive pattern, making the image...

Answer 29

dimmer

Question 30

phase plates contribute to constructive interference, making the image...

Answer 30

-brighter

Question 31

what is a phase plate?

Answer 31

-diffraction waves contributing to destructive interference undergo a phase change to make them constructive

Question 32

what is a hybrid lens?

Answer 32

a single refractive lens with a phase plate imbedded on one side of its surface

Question 33

the zero order on a diffractive contact lens has what power?

Answer 33

-no power! if any, it is the base power for distance

Question 34

the first and other orders for a diffractive contact lenses has what power?

Answer 34

add power for near vision

Question 35

with diffractive lenses, what is the expected VA?

Answer 35

far: 20/20 near: 20/40

Question 36

what is dysphotopsia?

Answer 36

unwanted patterns onto the retina (blur the retinal image)

Question 37

what is positive dysphotopsia?

Answer 37

bright artifacts onto the retina (halos and glare)

Question 38

what is negative dysphotopsia?

Answer 38

blockage of light onto the retina (shadows and dark spot)

Question 39

fresnel's lens increases the luminosiy of the lighthouse lamp by a factor of...

Answer 39

4

Question 40

how does iridescence in nature work biology? chemistry?

Answer 40

biology: absorption at certain wavelengths and reflects at others Chemistry: interference, diffraction, scattering

Question 41

what is chitin?

Answer 41

-natral diffraction grating

Question 42

strength of iridescence depends on what?

Answer 42

groove density and surface quality | -high groove density and smooth surface means stronger interference

Question 43

unlike conventional imaging, holographic imaging...

Answer 43

light from each point on the object will reach all points on the film

Question 44

for holographic imaging, what kind of image is formed at m=1? m=-1? which one is usually viewed?

Answer 44

m=1: real image, not usually viewed | m=-1: virtual image, usually viewed

Question 45

in holographic imaging, when will you see a 3D image and when will you see a rainbow image?

Answer 45

horizontally viewed: 3D | Vertically viewed: rainbow

Question 46

for a perfect eye, a larger pupil means....

Answer 46

a smaller image

Question 47

for a typical eye, a larger pupil means....

Answer 47

a larger image

Question 48

what size pupil will give you the best retinal image?

Answer 48

3mm