Physics The Human Eye (lesson 10)

Question 1

The human eye is a complex structure that

Answer 1

allows us to see

Question 2

Light rays from objects will enter the

Answer 2

eye and converge on the back of the eye
where clear images are formed

Question 3

Cornea –

Answer 3

allow lights to enter the eye and refracts light on to the lens

Question 4

Lens –

Answer 4

refracts light so it hits the retina

Question 5

(lens + cornea =

Answer 5

converging lens that produces a smaller , real , inverted image
on retina)

Question 6

Pupil –

Answer 6

the hole of the eye that allows light in

Question 7

Iris –

Answer 7

a ring that controls the size of the pupil and how much light enters your
eye

Question 8

Ciliary Muscles –

Answer 8

control the
shape of the lens; allow to
accommodate/refocus on an object

Question 9

Retina –

Answer 9

converts the light signal into electrical
signal that is transmitted to the brain through the
optic nerve

Question 10

Photoreceptive cells in the retina are referred to
either as

Answer 10

“rods” or “cones”

Question 11

Rod cells are more sensitive to

Answer 11

low light
(therefore night vision)

Question 12

Cone cells detect either

Answer 12

red, green, or blue
wavelengths of light
(therefore colour vision)

Question 13

To see clearly, an image has to form

Answer 13

right on the retina

Question 14

The ciliary muscles change the shape of the eye lens slightly to

Answer 14

focus on distant and
nearby object

Question 15

When a person’s eyes cannot focus on objects at every distance it results

Answer 15

in blurred
vision

Question 16

What does it mean to be 20/20?

This number is a measure of visual
acuity and compares your vision with

Answer 16

that of the average

Question 17

First number: your vision at
Second number:

Answer 17

your vision at 20ft
what the average
person sees at 20ft

Question 18

Normal vision: 20/20 –

Answer 18

this means the test
subject sees the line of letters at 20ft as if
the average person was standing 20ft from
the letters

Question 19

Poorer vision: 20/40 –

Answer 19

– this means the test
subject sees the line of letters at 20ft as if
average person was standing 40ft from the
letters

Question 20

Better vision: 20/10 –

Answer 20

this means the test
subject sees the line of letters at 20ft as if
the average person was standing 10ft from
the letters

Question 21

There are two main problems related to vision:

Answer 21

Hyperopia (far-sightedness)

Myopia (near-sightedness)

Question 22

Hyperopia (far-sightedness)

Answer 22

Have difficulty seeing nearby objects

Question 23

Hyperopia -Causes:

Answer 23

Shape: the distance between the lens and the retina is too small

Strength: the cornea-lens combination is too weak

Question 24

Presbyopia

Answer 24

is a form of far-sightedness caused by aging

Question 25

Hyperopic eyes focus images

Answer 25

behind the retina

Question 26

What lens can help focus the image onto the retina? -Hyperopic

Answer 26

The solution is a converging lens

To converge the rays before they go through the
lens of the eye

The rays can cross sooner to have an image form on
the retina

Question 27

Myopia (near-sightedness)

Have difficulty seeing

Answer 27

distant objects

Question 28

Myopia-Causes:

Answer 28

Shape: the distance between the lens and the retina is too large

Strength: the cornea-lens combination is too strong

Question 29

Myopic eyes focus images in

Answer 29

front of the retina

Question 30

What lens can help focus the image onto the retina?-Myopia

Answer 30

The solution is a diverging lens
To diverge the rays before they go through the lens
of the eye

The rays can cross later to have an image form on
the retina

Question 31

How do I find out if a person wearing glasses is far-sighted or near-sighted?

You may look at the shape of the lens:

Answer 31

1) far-sighted need to converge rays sooner so they will see blurry nearby objects (lens is thicker
in the middle)

2) near-sighted need to converge rays later so they will see blurry distant objects (lens is thick on
the edges)

Question 32

What two (2) parts of the eye refract light? Where must the light rays meet to produce a clear
image?

Answer 32

The two (2) parts of the eye that refract light are: the cornea and lens.
They must refract light onto the retina to produce a clear image.

Question 33

There are two (2) conditions of the eye. List the conditions and identify the problems with
each.

Answer 33

hyperopia: the individual is unable to clearly focus nearby objects; light rays meet behind the retina
myopia: the individual is unable to clearly focus distant objects; light rays meet in front of the retina

Question 34

The eye focuses light on the retina. The camera focuses light on the film. Discuss how the eye
and camera focus light differently.

Answer 34

In order to form a clear image, the eye must change the shape of the lens in order to refract light onto
the retina.
In order to form a clear image, the camera must move the lens along the principle axis in order to
refract light onto the film.