The retina – the light detector of the eye, Physics

Assignment Help:

The retina – the light detector of the eye:


The physical aspects of the retina:
1.The absorption of a light photons in a photoreceptor triggers an electrical signal to the brain-an action potential fig(4).
2. The energy of the photon is about 3 eV: the action potential has an energy millions of times greater.
3. The light photons apparently causes a photo chemical reaction in the photoreceptor which in some way initiates the action potential.
4.the photon must be above the minimum energy to cause the reaction.

 

1583_The retina – the light detector of the eye.png



The image on the retina is very small .A convenient equation for determining the size of the image on the retina comes from the ratios of the lengths of the sides of similar triangle fig (4).


O/P=I/Q


Where O is the object size ,I the image size ,P the object distant and Q the image distance usually about 2 cm. Fig(5)

 

1132_The retina – the light detector of the eye 2.png


There are two photoreceptor in the retina:

The cones and the rods .Though out most of the retina cones and rods are not on the surface of the retina but lie behind several layers of nerve tissue through which the light must pass fig(6) The rods and cones distributed symmetrically in all directions from the visual axis except in one region- the blind spot.

 

269_The retina – the light detector of the eye 3.png


-The rods are used for night or scayopic vision and for peripheral vision, they are much more abundant than the cones(~120 million in each eye).
- The rods are most sensitive to blue- green light(~510 nm).

The blind spot: It is a region from about 13o to 18o  that has neither cones nor rods ,this is the point at which the optic nerve.


-The cones (~ 6.5 million in each eye),they are primarily used in day light or photopic vision.
- With cones we can see fine details  and recognize deferent colors.
- The cones are not uniformly sensitive to all colors but have maximum sensitivity at about 550 nm in the yellow- green region .


Related Discussions:- The retina – the light detector of the eye

Define thermometry, The temperature of a body is measured indirectly by mak...

The temperature of a body is measured indirectly by making use of the fact that certain physical property of a substance changes linearly with the temperature If the value of th

Electronics 1, norton theorem and its application and uses in sciences

norton theorem and its application and uses in sciences

Define the magnets, Define the Magnets Magnets work according to rules ...

Define the Magnets Magnets work according to rules similar to electric charges. All magnets have two poles, north (actually north-seeking) and south poles. Like poles repel and

Kinematics., a ball is thrown horizontally from a point 100 m above the gro...

a ball is thrown horizontally from a point 100 m above the ground with a speed of 20 m/sec .find the time it takes to reach the ground...

What is the ohm law, What is the Ohm Law? Ohm discovered that the amoun...

What is the Ohm Law? Ohm discovered that the amount of current was directly proportional to the voltage (more voltage gives more current) and inversely proportional to the resi

Motion in one dimension and vectors, two forces f1 500Ndue east and f2 250N...

two forces f1 500Ndue east and f2 250N due north have their common initial point f1 - f2 is

Specific latent heat, explain specific latent heat of fusion with formula

explain specific latent heat of fusion with formula

Find the period of rotation of the rod, The record for the highest speed ac...

The record for the highest speed achieved in laboratory for a uniformly rotating object was 2.01*10^3 m/s for a0.15-m long carbon rod. What was the period of rotation of the rod?

Determine the wavelength of sound wave, Enrique Iglesias belts out a high-C...

Enrique Iglesias belts out a high-C (1024 Hz) from the deck of his yacht. What is the wavelength of this sound wave in the surrounding air? As the sound wave enters the ocean below

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd