Chapter 6 key words

Question 1

cornea

Answer 1

light rays are refracted by the cornea, thus helping to focus the light on the retina. The cornea does most of the focussing of the light rays.

Question 2

Iris

Answer 2

Controls the size of the pupil, thus regulating the amount of light that enters the eye. The iris is the coloured part of the eye.

Question 3

Pupil

Answer 3

A hole in the iris that light passes through to reach the retina.

Question 4

Sclera

Answer 4

The tough cover of the eyeball that forms the white part of the eye.

Question 5

Lens

Answer 5

Refines the refraction to further focus the light. The lens gets thicker and thinner depending on the distance of the object.

Question 6

Ciliary muscles

Answer 6

Controls the thickness of the lens. When the muscles contract, lens becomes thicker and focuses nearby objects.

Question 7

Retina

Answer 7

The area where the image is produced and converted into nerve signals.

Question 8

Optic Nerve

Answer 8

Carries the nerve signals to the brain.

Question 9

Astigmastism

Answer 9

Astigmatism is caused by an eye that isn’t completely round, which happens to everyone to a certain degree. When the eye isn’t perfectly round the light refracts in more than one direction than the other and only small parts of the image are clear. This can happen to objects that are near and far.

Question 10

Blind spot

Answer 10

The area where the optic nerve enters the retina does not have any light sensing cells. Thus creates a blind spot

Question 11

Laser light

Answer 11

A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term “laser” originated as an acronym for “light amplification by stimulated emission of radiation”.

Question 12

Refracting telescope

Answer 12

a telescope that uses a converging lens to collect light.

Question 13

Reflecting telescope

Answer 13

a telescope in which a mirror is used to collect and focus light.

Question 14

Total internal reflection

Answer 14

Total internal reflection is a phenomenon that happens when a propagating wave strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal to the surface.

Question 15

When the convex lens is more than 2 focal lengths away from the object, how will the image look?

Answer 15

The image will be upside down and smaller.

Question 16

When the convex lens is between 1 and 2 focal lengths away from the object, how will the image look?

Answer 16

The image will be upside down and larger

Question 17

When the concave lens is more than 2 focal lengths away from the object, how will the image look?

Answer 17

Upright and smaller

Question 18

When the concave lens is between 1 and 2 focal lengths away from the object, how will the image look?

Answer 18

Smaller and upright

Question 19

A concave lens refracts _____ ______ the normal

Answer 19

Away from

Question 20

Mirror that curves outwards

Answer 20

Convex

Question 21

If the object is mire than two focal lengths from a convex lens, it will appear to be _________

Answer 21

Smaller

Question 22

The focal ________ is the distance from the centre of the lens to where light rays converge

Answer 22

Length

Question 23

Light rays coming together

Answer 23

Converging

Question 24

A concave lens is _________ in the middle

Answer 24

Thinner

Question 25

Light rays meet at the focal ________

Answer 25

Point

Question 26

If the object is one or more focal lengths from a convex lena, it will appear to be ________

Answer 26

Upside down

Question 27

A convex lens refracts light rays _______ the normal

Answer 27

Towards

Question 28

Images formed by concave lenses are always smaller and __________

Answer 28

Upright

Question 29

A concave lens is ________ at the edges

Answer 29

Thicker

Question 30

Light rays spreading apart are called:

Answer 30

Diverging

Question 31

A mirror that curves inwards is called:

Answer 31

Concave

Question 32

How does the image form in the eye?

What are the names of the cells that receive the signals?

Answer 32

The image is produced on the retina. The cells in the retina change the image into electrical signals. ( upside down). The 2 types of light receptor cells- rods and cones

Question 33

What are the rods for?

Answer 33

B and W - 120 million per eye. Sensitive to the level of light

Question 34

What are cones for?

Answer 34

Colours- 6 million per eye. Sensitive to colour. Has three kinds of cells, each processing red, green and blue.

Question 35

What is myopia?

Answer 35

Nearsightedness, where the light entering the eye is not focussed properly thus making objects that are distant blurry. Caused when the eyeball is too long or the cornea is too curved.

Question 36

what is hyperopia?

Answer 36

Farsightedness- a common refractive error where the distant objects may seem more clearly than objects that are near. It is caused when your lens sits further back then it should or if your cornea is not curves enough.

Question 37

What is colour blindness?

Answer 37

A defect in the retina that affects the ability to distinguish colours. Usually one or more of the cone cells are missing. Either inherited or a result of aging.

Question 38

What are the statistics of myopia, hyperopia, astigmatism and colour blindness?

Answer 38

Myopia - 30% of Canada
Hyperopia- 1 in 4 americans
Astigmatism- 16.67% of the USA
Colour blindness- men: 8%, women: less than 1%

Question 39

Nearsighted glasses, telescopes

Answer 39

What are some uses for concave lenses?

Question 40

What are some uses for convex lenses?

Answer 40

Farsighted glasses