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Related Concept Videos

Color Vision01:24

Color Vision

1.9K
Color perception begins in the retina, the light-sensitive layer at the back of the eye. Two main theories explain how colors are seen: the trichromatic theory and the opponent-process theory. The trichromatic theory, proposed by Thomas Young in 1802 and extended by Hermann von Helmholtz in 1852, suggests that color vision is based on three types of cone receptors in the retina. These cones are sensitive to different but overlapping ranges of wavelengths corresponding to red, blue, and green.
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IR Frequency Region: Fingerprint Region01:03

IR Frequency Region: Fingerprint Region

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IR spectra are divided into two main regions: the diagnostic region and the fingerprint region. The diagnostic region of the spectrum lies above 1500 cm−1. The absorptions resulting from single-bond vibrations of the N–H, C–H, and O–H stretch at higher wavenumbers and appear on the left side of the spectrum. The stretching absorptions of the C≡C and C≡N occur between 2100–2300 cm−1. In contrast, those arising from stretching absorptions of the...
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Photoreceptors and Visual Pathways01:22

Photoreceptors and Visual Pathways

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At the molecular level, visual signals trigger transformations in photopigment molecules, resulting in changes in the photoreceptor cell's membrane potential. The photon's energy level is denoted by its wavelength, with each specific wavelength of visible light associated with a distinct color. The spectral range of visible light, classified as electromagnetic radiation, spans from 380 to 720 nm. Electromagnetic radiation wavelengths exceeding 720 nm fall under the infrared category,...
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IR Spectrum01:19

IR Spectrum

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When infrared (IR) radiation passes through a molecule, the bonds stretch or bend by absorbing the radiation. This absorption creates the molecule's absorption spectrum, which is the plot of its percentage transmittance versus wavenumber.
Transmittance is defined as the ratio of the radiant power passing through a sample to that from the radiation's source. Multiplying the transmittance by 100 gives the percent transmittance (%T), which varies between 100% (no absorption) and 0%...
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Indicators02:39

Indicators

62.4K
Certain organic substances change color in dilute solution when the hydronium ion concentration reaches a particular value. For example, phenolphthalein is a colorless substance in any aqueous solution with a hydronium ion concentration greater than 5.0 × 10−9 M (pH < 8.3). In more basic solutions where the hydronium ion concentration is less than 5.0 × 10−9 M (pH > 8.3), it is red or pink. Substances such as phenolphthalein, which can be used to determine the pH of a solution, are...
62.4K
Fixation and Sectioning01:03

Fixation and Sectioning

8.8K
Two basic types of preparation are used to visualize specimens with a light microscope: wet mounts and fixed specimens.
The simplest type of preparation is the wet mount, in which the specimen is placed in a drop of liquid on the slide. A liquid specimen can be directly deposited on the slide using a dropper. Solid specimens, such as skin scraping, can be placed on the slide before adding a drop of liquid to prepare the wet mount. Sometimes the liquid is simply water, but stains are often added...
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Measuring Spatially- and Directionally-varying Light Scattering from Biological Material
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IRIS COLOUR CLASSIFICATION SCALES--THEN AND NOW.

Mariana Grigore, Alina Avram

    Romanian Journal of Ophthalmology
    |July 5, 2016
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    Summary
    This summary is machine-generated.

    Iris color classification has evolved from subjective comparisons to objective, automated systems. However, a universally accepted standard for iris color remains elusive despite its importance in various scientific fields.

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    Area of Science:

    • Ophthalmology
    • Anthropology
    • Genetics

    Background:

    • Eye color is a key human phenotypic trait.
    • Historically, iris color classification relied on subjective comparisons using painted eyes or early photographs, lacking standardization and reproducibility.
    • Existing scales have varied categories and often suffer from color variability and lack of objective measurement.

    Purpose of the Study:

    • To review the historical evolution of iris color classification systems.
    • To highlight the limitations of traditional methods and the advent of objective, automated approaches.
    • To underscore the ongoing need for a universally accepted iris color classification scale.

    Main Methods:

    • Historical review of iris color classification scales from 1843 to present.
    • Analysis of technological advancements including spectrophotometry and digital image analysis.
    • Evaluation of the objectivity, accuracy, and reproducibility of different classification methods.

    Main Results:

    • Early scales were subjective and lacked standardization.
    • Photography improved objectivity but introduced print variability.
    • Automated systems (spectrophotometry, digital analysis) offer accuracy but are costly and research-limited.
    • No single iris color classification scale has achieved widespread acceptance.

    Conclusions:

    • Iris color classification has progressed significantly with technology, moving towards objective methods.
    • Despite advancements, a universally accepted, standardized iris color scale is still lacking.
    • Further development is needed to create a practical, objective, and widely adopted system for iris color classification.