Lecture 6

Question 1

Name the red area

Answer 1

Blind Spot

Where the optic nerve leaves the eye

Question 2

What is the Macula (yellow spot)?

Answer 2

Situated on the optical axis, contains the fovea centralis. The area of most acute vision.

Contains densly packed cones only

Question 3

Rotation of the eye allows…

Answer 3

Objects to be imaged on the fovea centralis

Question 4

Why is the largest degree of light bending in the cornea?

Answer 4

The cornea has the smallest radius of curvature (0.8mm)

Change in refraction index is largest when light enters the aqueus humour from the air.

Question 5

What is the purpose of the crystaline lens in the eye?

Answer 5

For fine adjustment of focus on objects at different distances.

Question 6

What is the ‘far point’?

Answer 6

The most distant point the eye can focus on. Normally infinity

Question 7

The closest point clearly visible to the eye

Answer 7

0.25m (‘Near Point’)

Question 8

What is the image distance for the eye?

Answer 8

s’ = 0.020m

Question 9

What is visual acuity?

Answer 9

The fineness of details discernible by the eye

Question 10

What is required to distinguish two distincy small objects?

Answer 10

At least one non excited cone must be located between two excited cones.

Question 11

Visual acuity decreases as…

Answer 11

You move further from the fovea centralis.

Question 12

The minimum intensity needed to see a flash of light is known as

Answer 12

Threshold intensity

Question 13

Cones are only active in…

While cones are

Answer 13

1. Light adapted vision
2. Always active

Question 14

The sensation of colour is perceived only in the…

Answer 14

Light adapted eye

Question 15

Operating at low light intensities, the … do not register colour.

Answer 15

Rods

Question 16

Give the photo sensitive pigment and peak sensitivities of the:

Red Cone

Green Cone

Blue Cone

Answer 16

Pigment Erythrolabe (575nm)

Pigment Chlorolabe (535nm)

Pigment Cycanolabe (445nm)

Question 17

Complimentary colours produce…

Answer 17

White light

Question 18

Normal Vision is known as…

Answer 18

Emmetropia

Question 19

Short-sightedness is known as…

Answer 19

Myopia

Where the power of the eye it too great

Question 20

Far-sightedness is known as

Answer 20

Hypermetropia

• Where the power of the eye is too low*
• Caused by the lens reaching adult size before the rest of the eyeball*

Question 21

Condition where the lens of the eye hardens with age and becomes too stiff to accomodate.

Answer 21

Presbyopia

Question 22

What is astigmatism?

Answer 22

Uneven curvature of the cornea, planes of light can be focused better than others.

Question 23

Formula to calculate the angular magnification

Answer 23

Question 24

Formula to calculate the final overall magnification

Answer 24

Question 25

Calculate the form of a sinusoidal wave.

Answer 25

Question 26

Visible light is a specturem found between the wavelengths of…

Answer 26

400 - 700 nm

Question 27

What is the principle of superposition?

Answer 27

When two or more waves pass the same point, the resulting wave is the amplitude sum of the individual waves.

Question 28

When waves are in phase, they…

When waves are out of phase, they…

Answer 28

1. Enforce eachother
2. Weaken eachother (Interference)