Lecture 2 - Duplex Retina Flashcards
A source with which of the following color temperature will appear most red?
2000K
The color temperature of an incandescent bulb is 3300K. This means that:
The bulb’s spectral distribution matches that of a blackbody radiator whose temperature is 3300K
A neutral density filter transmits 50% of 450nm light that is incident upon it. If 40W of 550nm are incident on the filter, how many watts are transmitted?
20
The least amount of distortion is present with sunglasses made with a:
Neutral-density filter
Which of the following light sources has more energy concentration in the blue region of the spectrum?
LEDs
What makes it possible for the human eye to see something very bright and something very feeble in the night sky?
The pupil, by changing its diameter in response to light, helps to control the amount of light that falls upon the retina (in sun, it gets smaller; in dark, it gets bigger)
Consider a white page with a luminance of 100 nits. Compute the retinal illuminance for a 9-mm diameter pupil
td = (nits) x (pupil area in mm)
Pupil area = (pi)r^2 = (3.14)(4.5)^2 = 63.62 mm^2
td = (100)(63.62) = 6,362 td
Consider a white page with a luminance of 100 nits. Compute the retinal illuminance for a 2-mm diameter pupil
td = (nits) x (pupil area in mm)
Pupil area = (pi)r^2 = (3.14)(1)^2 = 3.14 mm^2
td = (100)(3.14) = 314 td
What is the ratio of retinal illuminations between a 9-mm pupil and a 2-mm pupil?
20:1 (about equal to 1.3 log units = 13dB)
How can the eye adjust to a 10-log unit range of retinal luminance if the pupil only accounts for 1.3 log units at max?
About 10% is how much the pupil has an effect for your retinal luminance
Since pupillary diameter only accounts for about 10% of retinal illuminance (adaptation), where does the remaining adaptation come from?
The existence and properties of 2 classes of retinal photoreceptors, rods and cones
Scotopic vision occurs under what kind of lighting conditions?
Dim
VA for scotopic vision?
Poor VA (20/200 vision)
What does scotopic vision have an absence of?
Color discrimination due to no cones being activated
Scotopic vision is mediated by what?
Rods
Photopic vision occurs under what kind of lighting conditions?
Bright light
VA’s for photopic vision
Excellent VA’s (20/20)
What does photopic vision have that scotopic vision does not?
Color discrimination (no rods are activated)
What mediates photopic vision?
Cones
What is meant by a duplex retina?
The existence of 2 classes of photoreceptors, each operating under different lighting conditions
What contributes to vision under mesopic (twilight) conditions?
Both rods and cones
What photopigment is contained within the discs of the rod’s outer segment?
Rhodopsin
How many rods does one eye contain?
120 million rods
How many disks does one rod contain?
1000
How many rhodopsin molecules does one disk contain?
10,000
The absorption of how many photons is sufficient to activate a rod?
1
This is the first step in a sequence of events that ultimately leads to vision, where the absorption of light quanta by the photosensitive pigment in the outer segment causes the photoreceptor to become what?
Hyperpolarized
Step one towards vision
Hyperpolarized
