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Accommodation is the process by which the vertebrate eye changes optical power to maintain a clear image or focus on an object as its distance varies. In this, distances vary for individuals from the far point —the maximum distance from the eye for which a clear image of an object can be seen, to the near point —the minimum distance for a ...
Transparent eyeball. The transparent eyeball is a philosophical metaphor originated by American transcendentalist philosopher Ralph Waldo Emerson. In his essay Nature, the metaphor stands for a view of life that is absorbent rather than reflective, and therefore takes in all that nature has to offer without bias or contradiction.
Health effects of sunlight exposure. Exposing skin to the ultraviolet radiation in sunlight has both positive and negative health effects. On the positive side, exposure allows for the synthesis of vitamin D 3. Vitamin D has been suggested as having a wide range of positive health effects, which include strengthening bones [ 1] and possibly ...
The human eye can function from very dark to very bright levels of light; its sensing capabilities reach across nine orders of magnitude. This means that the brightest and the darkest light signal that the eye can sense are a factor of roughly 1,000,000,000 apart. However, in any given moment of time, the eye can only sense a contrast ratio of ...
Depth perception. Perspective, relative size, occultation and texture gradients all contribute to the three-dimensional appearance of this photo. Depth perception is the ability to perceive distance to objects in the world using the visual system and visual perception. It is a major factor in perceiving the world in three dimensions.
The retina (from Latin rete 'net'; pl. retinae or retinas) is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs.The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then processes that image within the retina and sends nerve impulses along the optic nerve to the visual cortex to create visual perception.
The functional unit of the eye is the photoreceptor cell, which contains the opsin proteins and responds to light by initiating a nerve impulse. The light sensitive opsins are borne on a hairy layer, to maximise the surface area. The nature of these "hairs" differs, with two basic forms underlying photoreceptor structure: microvilli and cilia. [26]
Internal perception ( proprioception) tells us what is going on in our bodies; where our limbs are, whether we are sitting or standing, whether we are depressed, hungry, tired and so forth. External or sensory perception ( exteroception ), tells us about the world outside our bodies. Using our senses of sight, hearing, touch, smell, and taste ...