Vision is one of the sensory systems that allows living beings to gather information about their surroundings. The visual system captures incident light either from an object emitting it or reflecting it, and the light is converted into an electrical signal after interacting with special cells in the eyes. The complete vision process is one of the most interesting and complex physico-biological processes, and its study has allowed us to solve medical problems in the human eye.
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Jetzt kostenlos anmeldenVision is one of the sensory systems that allows living beings to gather information about their surroundings. The visual system captures incident light either from an object emitting it or reflecting it, and the light is converted into an electrical signal after interacting with special cells in the eyes. The complete vision process is one of the most interesting and complex physico-biological processes, and its study has allowed us to solve medical problems in the human eye.
Light is composed of photons, which can behave as particles or waves. Each photon has a frequency that corresponds to the energy of the photon. The process by which photons form an image in our brain is quite complex, but we can break it down as follows:
Below we look at the structure of the human eye and how we can see.
The eye is a complex organ composed of lenses, muscles, nerves, and tissue. It captures incident light and converts it into an electrical signal that is sent to the brain. Here are some of the main parts of the eye:
Let’s briefly study how we are able to see!
A certain amount of light is needed in order for us to see. An aperture called the pupil regulates the amount of light entering the eye. This aperture is circular, and you can see it as black when you look at your eyes in the mirror.
The radius of the aperture is regulated by the iris, which is connected to the ciliary muscle. The muscle will expand and contract depending on the light conditions. When the intensity is higher, the muscles will contract, and when it is lower, the muscles will expand.
Light entering the eye passes through the cornea. The cornea will alter its shape depending on the object’s distance. In this case, when the ciliary muscle contracts, it changes the shape of the lenses, and this will change the distance at which we can focus an object.
The photodetector in the eye is the retina. There are around 130 million light-sensitive cells in it. Each cell reacts to light from a single small point. A photopigment is a substance found in light-sensitive cells. The photopigment molecules absorb light and excite the cell, resulting in an electrical impulse that travels through a network of neurons to the optic nerve and, ultimately, the brain.
There are two main types of light-sensitive cells: rods and cones.
The human eye can capture images in both dark and bright environments. The pupil opens to around 8mm in low light and contracts to 1.5mm when exposed to higher luminosity.
Rod and cone cells can detect electromagnetic waves with wavelengths ranging from 380 nanometres to 750 nanometres (nm). Rod cells are sensitive to nearly the whole wavelength range, with a peak response at 500nm. Cone cells, on the other hand, contain one of three photopigments, each with a particular frequency/wavelength range of response with its own peak and reception.
One of these photopigments in a cone cell may absorb a photon of light when it reaches the retina. The wavelength of the light influences the likelihood of absorption. A certain wavelength will excite one of the three types of cone cells in a specific ratio. This allows the brain to recognise wavelengths and generate the colour sense.
The spatial resolution of an eye is its ability to see an object in greater detail. In the human eye, this resolution equals about one arc per minute, which is one degree between 160. This resolution allows us to see objects at one kilometre, which are separated by no less than 30cm. If we use the analogy of a camera, the overall resolution of the human eye is more than 576 megapixels per eye.
1. Diagram showing the parts of the eye. https://commons.wikimedia.org/wiki/File:Diagram_showing_the_parts_of_the_eye_CRUK_326.svg
2. Overview of the retina photoreceptors. Spectral sensitivities of the photoreceptors in the human eye. https://commons.wikimedia.org/wiki/File:Overview_of_the_retina_photoreceptors_(b).png
The eye works as follows: Light enters the eye through the cornea. The cornea, being a refractive medium, bends the light entering the eye, which then passes through the pupil and enters the lens. Once the light enters the lens, the lens adjusts the focal length based on the distance to the object. The image is formed on the back of the eye at the retina. The signal is picked up by special cells, which use different pigments. Each pigment reacts differently to a different photon frequency. The signal is transmitted to the brain as an electrical impulse via the optic nerve.
Vision is one of the sensory systems that allows living beings to gather information about their surroundings. The visual system captures incident light either from an object emitting it or reflecting it, and the light is converted into an electrical signal after interacting with special cells in the eyes.
Vision and how we see works as follows: The eye works as follows: Light enters the eye through the cornea. The cornea, being a refractive medium, bends the light entering the eye, which then passes through the pupil and enters the lens. Once the light enters the lens, the lens adjusts the focal length based on the distance to the object. The image is formed on the back of the eye at the retina. The signal is picked up by special cells, which use different pigments. Each pigment reacts differently to a different photon frequency. The signal is transmitted to the brain as an electrical impulse via the optic nerve.
What is needed for the creation of an image?
Both are correct answers.
What controls the amount of light entering the eye?
Pupil.
Which eye part regulates the radius of the pupil?
Iris.
What is the cornea?
It is a transparent membrane covering the front portion of the eye.
By what range does the pupil contract and expand?
The pupil expands to around 8mm in low light and contracts to 1.5mm in strong light.
What is a photopigment?
A photopigment is a substance found in light-sensitive cells known as cone cells.
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