Unit 2 - Optics and Light (Part 2)

Question 1

Sclera -

Answer 1

• the white, tougher outer wall of the eye

- keeps the eyes shape and protects its delicate internal parts

Question 2

Cornea -

Answer 2

• transparent layer at the front of the eye

- refracts the most light, helps focus light onto retina

Question 3

Iris -

Answer 3

• coloured part of the eye
• controls amount of light entering pupil
• makes the pupil large when light is dim
• makes pupil small when light is bright

Question 4

Pupil -

Answer 4

• the hole in the iris
• light passes through pupil to reach retina
• can dilate (get smaller) if too much light

Question 5

Lens -

Answer 5

• converging (convex) lens that gathers light

- helps focus light into retina

Question 6

Ciliary muscles -

Answer 6

• controls thickness of the lens to adjust for near and far objects
• contract to make lens thicker, to see up close objects
• relax, lens is normal shape (thinner) to see far away objects

Question 7

Retina -

Answer 7

• the area where the image is produced and converted into nerve signals
• contains light receptor cells: cone cells, to detect colour and detail and rod cells, sensitive to dim light

Question 8

Fovea-

Answer 8

-highest concentration of cone cells

Question 9

Optic nerve-

Answer 9

-carries nerve signals to the brain

Question 10

Virtreous gel -

Answer 10

-clear gel (mostly water) that fills the space between the lens and the retina of the eyeball

Question 11

Calculation reflection formula:

Answer 11

V = a
N = ?
C = 3.0x10(8)m/s

Question 12

Calculating the formula for speed of light:

Answer 12

N = a
V = ?
C = 3.0x10(8)m/s

Question 13

Differences between real and virtual images:

Answer 13

• Real images appear inverted, virtual images appear right
• Real images can be obtained on a screen, virtual images cannot be seen on a screen
• In case of mirrors, real image lies in front while virtual image lies behind the mirror
• In case of lenses, real image lies on the other side of the object whereas virtual image lies on the same side of the object

Question 14

Real image:

Answer 14

Rays of light come together to make an image

Question 15

Virtual image:

Answer 15

No rays of light at image location, it only appears that rays of light come from the image

Question 16

Total internal reflection:

Answer 16

As light encounters a boundary between 2 media, some light reflects and some refracts.

Two conditions must be met in order for total internal reflection to happen:

1. Light must be travelling from a slow to fast medium
2. The angle of incidence must be more than the critical angle

Eg. Prisms used in periscopes

Question 17

Medium-

Answer 17

Any physical substance through which energy can be transferred

Question 18

Name all rays/angles in a reflection diagram , from left to right:

Answer 18

Incident ray, angle of incidence, the normal, angle of reflection, reflected ray

Question 19

Why do objects in water appear to be at a different location than they actually are?

Answer 19

As light passes from one substance into another, it will travel straight through with no change of direction when crossing the boundary between the two substances. However, if the light impacts the boundary at any other angle it will be bent or refracted. As an example, if a beam of light enters water at a slight angle it will be refracted to a very small degree. If the angle of the beam is increased even farther, the light will refract with increasing proportion to the entry angle, which cause the object to be seen by the human eye in a different location.

Question 20

Far-sighted:

Answer 20

The eye cannot refract light well enough to form an image on the retina so the image is projected farther behind the retina. This can be corrected with converging type lens.

Question 21

Near-sighted:

Answer 21

The eye cannot refract light well enough to form an image on the retina and the image is projected farther in front of the retina compared to a healthy eye. This can be corrected with diverging type lens.