Week 9

Question 1

Light is an electromagnetic wave (EM) (meaning)

Answer 1

light is self-propagating combination of oscillating electric and magnetic fields

Question 2

The speed of light (or any electromagnetic wave) for observers:

Answer 2

It is the same for all observers, regardless of their direction or speed.

Question 3

Visible light lies on the spectrum

Answer 3

between about 380 nm and 750 nm

Question 4

refraction -

Answer 4

phenomenon of when a ray of light is transmitted obliquely through the boundary between two materials of unlike index of refraction, the ray bends

Question 5

absolute index of refraction of a material:

Answer 5

n = speed of light in vacuum / speed of light in the meterial = c/v

Question 6

For any two material, the relative index of refraction of material 1 with respect to material 2 is:

Answer 6

relative index = n1/n2,

n - the absolute refractive indices of the two materials

Question 7

If n2 > n1, the ray bends

Answer 7

toward the normal

Question 8

If n2 < n1, the ray bends

Answer 8

away from the normal

Question 9

if n2 = n1, refraction

Answer 9

does not bend the light beam

Question 10

Snell’s Law:

Answer 10

The way in which a ray refracts at an interface between materials with indices of refraction ni and nr

ni x sinΘi = nr x sinΘr

Question 11

reflection -

Answer 11

when light hits the surface of almost any material, some of that light ‘bounces back’ off the surface

Question 12

law of reflection:

Answer 12

reflected light leaves the surface at the same angle that the incident light falls on it

Question 13

Specular reflection -

Answer 13

happens when light hits a very flat, reflective surface, such as a mirror => all light coming from a single direction is reflected in a single direction.

Question 14

diffuse reflection

Answer 14

when the surface is rough, the light is reflected in a wide range of directions

Question 15

Converging or positive lenses:

Answer 15

• thicker at the center than at the rim
• converge a beam of parallel light to a real focus

Question 16

Diverging or negative lenses

Answer 16

• thinner at the center than at the rim.
• diverge a beam of parallel light from a virtual focus

Question 17

Converging lenses form

Answer 17

inverted real images of objects located outside the principal focus

Question 18

Diverging lenses produce

Answer 18

only virtual, erect and smaller images of real objects

Question 19

Within the eye the cornea and crystalline lens are what kind of lenses?

Answer 19

positive lenses, because they need to form a real image on the retina.

Question 20

radius of curvature, r, is positive when

Answer 20

its center of curvature lies to the right of the surface

Question 21

radius of curvature, r, is negative when

Answer 21

its center of curvature lies to the left of the surface

Question 22

for positive focal lengths, lenses can be:

Answer 22

biconvex, planoconvex (one side flat) or positive
meniscus

Question 23

for negative focal lengths, lenses can be:

Answer 23

biconcave, planoconcave (one side flat), or negative meniscus

Question 24

isolated cornea is what type of lens?

Answer 24

negative meniscus lens

Question 25

crystalline lens is what type of lens?

Answer 25

an asymmetric biconvex lens

Question 26

Why is cornea transparent?

Answer 26

because it is uniform in structure, avascular except in the extreme periphery, and relatively dehydrated

Question 27

layer of tears covering cornea - how thick and fn?

Answer 27

7–10 µm thick

smoothens over optical irregularities and supplies the cornea with oxygen

Question 28

diameter of the pupil is controlled by

Answer 28

opposing pair of smooth muscles

Question 29

formation of an image on the retina is determined by (2):

Answer 29

1. the indices of refraction of each eye component that the light passes through and
2. by the shapes of the surfaces of these elements

Question 30

focusing elements in the eye

Answer 30

cornea and crystalline lens

Question 31

performance of focusing in the eye:

Answer 31

cornea performs about two-thirds of the focusing and the crystalline lens the remaining one-third

Question 32

rod cells: how many, characteristics, fn, where, sensitivity in nm

Answer 32

• about 120 million rod cells per retina
• high sensitivity, low spatial acuity
• night vision, peripheral vision
• relatively more numerous in the periphery of the retina
• sensitivity of rods peaks near 500 nm => vision using only rods results in various shades of gray.

Question 33

cells: how many, characteristics, fn, where, sensitivity in nm

Answer 33

• about 6.5 million cone cells per retina
• low sensitivity—about 1.000× lower than rods—high spatial awareness
• concentrated in the fovea
• blue cones: 445 nm, green cones 535 nm, red cones 570 nm

Question 34

Most of the light from 300 to 400 nm is absorbed by

Answer 34

crystalline lens

Question 35

accommodation -

Answer 35

The ability to control the focal length of the crystalline lens

Question 36

Decreasing the pupil size affects vision in several ways (3):

Answer 36

1. Decreasing pupil size decreases light transmission to the retina.
2. The size of the diffraction-limited spot varies inversely with opening diameter.
3. Decreasing pupil size lessens the effect of lens aberrations.

Question 37

depth of field

Answer 37

range in object distances over which good images are formed

Question 38

Myopia is corrected with a

Answer 38

diverging lens

Question 39

hyperopia is corrected w/

Answer 39

Converging lenses

Question 40

Keratoconus

Answer 40

condition in which the cornea thins near the center to form a cone and can be locally wavy because of corneal scarring