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Entoptic phenomena (from Ancient Greek ἐντός (entós) 'within' and ὀπτικός (optikós) 'visual') are visual effects whose source is within the human eye itself. (Occasionally, these are called entopic phenomena, which is probably a typographical mistake.) In Helmholtz's words: "Under suitable conditions light falling on the eye may ...
A labelled diagram of the major arteries and veins of the human body. Near-infrared vein finder are medical devices used to try to increase the ability of healthcare providers to see veins . [ 1 ] They use near-infrared light reflection to create a map of the veins. [ 1 ]
To obtain the pattern for the database record, an individual inserts a finger into an attester terminal containing a near-infrared light-emitting diode (LED) light and a monochrome charge-coupled device (CCD) camera. The hemoglobin in the blood absorbs near-infrared LED light, which makes the vein system appear as a dark pattern of lines. The ...
Haidinger's brush, more commonly known as Haidinger's brushes is an image produced by the eye, an entoptic phenomenon, first described by Austrian physicist Wilhelm Karl von Haidinger in 1844. Haidinger saw it when he looked through various minerals that polarized light. [1] [2] Many people are able to perceive polarization of light. [3]
Although water is nearly transparent in the range of visible light, it becomes absorbing over the near-infrared region. Water is a critical component since its concentration is high in human tissue. The absorption spectrum of water in the range from 250 to 1000 nm is shown in Figure 2.
One example of a pressure phosphene is demonstrated by gently pressing the side of one's eye and observing a colored ring of light on the opposite side, as detailed by Isaac Newton. [ 7 ] [ 8 ] [ 9 ] Another common phosphene is "seeing stars" from a sneeze , laughter, a heavy and deep cough, blowing of the nose , a blow on the head or low blood ...
Look up! A bright comet is expected to light up the sky this week. Comet Tsuchinshan-Atlas, also known as C/2023 A3, is making its way towards Earth and is expected to be visible to the naked eye ...
A rete mirabile (Latin for "wonderful net"; pl.: retia mirabilia) is a complex of arteries and veins lying very close to each other, found in some vertebrates, mainly warm-blooded ones. The rete mirabile utilizes countercurrent blood flow within the net (blood flowing in opposite directions) to act as a countercurrent exchanger .