Light and The Eye

Question 1

What is a light? How is it produced?

Answer 1

Form of electromagnetic radiation energy produced by vibrations of electrically charged material

Question 2

What are two ways to conceptualise light?

Answer 2

As stream of Photons and a wave

Question 3

What is the electromagnetic spectrum?

Answer 3

Range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies.

Question 4

Refraction of a wave of energy means

Answer 4

bending or spreading out of waves as they pass from one medium to another.

Question 5

Reflection

Answer 5

When light strikes a surface and bounces off at a well-defined angle

Question 6

When does transmission of light occur?

Answer 6

When light hits an object that is transparent , light can penetrate the material to travel all the way through

Question 7

What happens when light is transmitted?

Answer 7

It can be scattered or refracted

Question 8

Scattering

Answer 8

Phenomen by which a beam of light is redirected in many different directions when it interacts with a particle of matter.

Question 9

Cornea

Answer 9

The transparent “window” on the outer part of the eye that bends light to help the eye focus

Question 10

How are photons transmitted/absorbed in the cornea?

Answer 10

Most light photons are transmitted through the cornea rather than being reflected or absorbed, contains fibers and no blood vessels that would absorb light

Question 11

Aqueous Humor

Answer 11

Fluid derived from blood and supplies oxygen and nutrients to and waste from the cornea and the lens,

Question 11

Where is aqueous humour located?

Answer 11

Between the cornea and iris.

Question 12

Virteous Humor Location

Answer 12

Between lens and the retina

Question 13

Virteous Humor Function

Answer 13

Maintain the round shape of the eye

Question 14

Lens

Answer 14

Transparent and has no blood supply function is to transmit and focus light onto the retina

Question 15

What changes the shape of the lens?

Answer 15

shape of lens can be changed by ciliary muscles,

Question 16

Pupil

Answer 16

Allows light into your eye as the muscles of your iris change its shape

Question 17

Iris

Answer 17

Gives eyes its distinctive colour and controls the size of the pupil and the amount of light

Question 18

How does the pupil of the iris play an important role in the image quality?

Answer 18

Small pupils increase visual acuity, which improves discrimination of fine stimuli; and large pupils increase light influx, which improves detection of faint stimuli (less visual acuity)

Question 19

Role of Retina

Answer 19

Detect light and where light energy is turned into electrical neural signals- known as transduction

Question 20

What is the most powerful refractive surface of the eye?

Answer 20

Cornea is highly curved and has a higher refractive index than air, making it the most powerful refractive surface

Question 21

Presobiya

Answer 21

Inability to focus on nearby objects caused by loss of elasticity of the lens of the eye, occurring typically in middle and old age.

Question 22

What is a cataract and how does it interfere with vision?

Answer 22

Cloudy area of the eye and it interferes with vision by absorbing and scattering more light than the normal lens does

Question 23

What can correct agistiasm?

Answer 23

Lenses that have two focal points that provide different amounts of focusing power in the horizontal and vertical planes can correct astigmatism

Question 24

How can hyperopia be corrected?

Answer 24

Positive plus lenses which converge rays of light before they enter the eye

Question 25

Macula

Answer 25

The portion of eye at the center of the retina that processes sharp, clear, straight-ahead vision

Question 26

Fovea

Answer 26

Located in the center of the macula and responsible high-acuity vision it is densely saturated with cone photoreceptors.

Question 27

Optic Disc

Answer 27

• Entry point for major blood vessels that supply the retina
• Represents the beginning of the optic nerve (second cranial nerve) and is the point where the axons of retinal ganglion cells come together

Question 28

Why is the optic disc referred to as the blind spot?

Answer 28

There are no photoreceptors cells

Question 29

Why are photoreceptors in the back of the retina?

Answer 29

Light has to pass through layers of neurons and capillaries before it reaches the photosensitive sections of the rods and cones.

Question 30

Eccentricity:

Answer 30

Term referring to the angular distance from the centre of the visual field or from the foveola of the retina

Question 31

What happens as retinal eccentricity ( (i.e. the light of the image enters the eye at a larger angle and approaches peripheral vision) increases?

Answer 31

As retinal eccentricity increases, the observer is slower and less accurate to detect an item they are searching for.

Question 32

What conditions do rods and cones function best in?

Answer 32

Rods function well in dim (scoptic) illumination
Cones require brighter (photopic) illumination

Question 33

Why can rods not signal differences in colour?

Answer 33

They have the same type of photopigment (rhodopsin) which is found in rods and mainly in the stack of membranous discs in the outer membrane

Question 34

What are the three different photopigments in cones?

Answer 34

Small (blue), green (medium) long wavelength (red)

Question 35

Where do rods and cones get their energy from?

Answer 35

Retinal Pigment epithelium that lies below the retina

Question 36

Steps of Light Entering the Eye

Answer 36

1) Light enters the eye through the cornea
2)From the cornea, the light passes through the pupil. The iris controls the amount of light passing through.
3) From there, it then hits the lens and passes through the vitreous humor.
4) Finally, the light reaches the retina and the image is inverted.
5) The optic nerve is then responsible for carrying the signals to the visual cortex of the brain.
5) The visual cortex turns the signals into images (for example, our vision).