Lecture 6 Flashcards
Name the red area
Blind Spot
Where the optic nerve leaves the eye
What is the Macula (yellow spot)?
Situated on the optical axis, contains the fovea centralis. The area of most acute vision.
Contains densly packed cones only
Rotation of the eye allows…
Objects to be imaged on the fovea centralis
Why is the largest degree of light bending in the cornea?
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.
What is the purpose of the crystaline lens in the eye?
For fine adjustment of focus on objects at different distances.
What is the ‘far point’?
The most distant point the eye can focus on. Normally infinity
The closest point clearly visible to the eye
0.25m (‘Near Point’)
What is the image distance for the eye?
s’ = 0.020m
What is visual acuity?
The fineness of details discernible by the eye
What is required to distinguish two distincy small objects?
At least one non excited cone must be located between two excited cones.
Visual acuity decreases as…
You move further from the fovea centralis.
The minimum intensity needed to see a flash of light is known as
Threshold intensity
Cones are only active in…
While cones are
- Light adapted vision
- Always active
The sensation of colour is perceived only in the…
Light adapted eye
Operating at low light intensities, the … do not register colour.
Rods
Give the photo sensitive pigment and peak sensitivities of the:
Red Cone
Green Cone
Blue Cone
Pigment Erythrolabe (575nm)
Pigment Chlorolabe (535nm)
Pigment Cycanolabe (445nm)
Complimentary colours produce…
White light
Normal Vision is known as…
Emmetropia
Short-sightedness is known as…
Myopia
Where the power of the eye it too great
Far-sightedness is known as
Hypermetropia
- Where the power of the eye is too low*
- Caused by the lens reaching adult size before the rest of the eyeball*
Condition where the lens of the eye hardens with age and becomes too stiff to accomodate.
Presbyopia
What is astigmatism?
Uneven curvature of the cornea, planes of light can be focused better than others.
Formula to calculate the angular magnification
Formula to calculate the final overall magnification
Calculate the form of a sinusoidal wave.
Visible light is a specturem found between the wavelengths of…
400 - 700 nm
What is the principle of superposition?
When two or more waves pass the same point, the resulting wave is the amplitude sum of the individual waves.
When waves are in phase, they…
When waves are out of phase, they…
- Enforce eachother
- Weaken eachother (Interference)
