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Colors  UV – VIS spectroscopy

Colors  UV – VIS spectroscopy. Jakub Kovář  Jiří Stančík. Color and light. The starting point of an understanding of color is a description of light. White light is actually made up of a whole range of colours, mixed together We can see this if we pass white light through a glass prism.

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Colors  UV – VIS spectroscopy

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  1. ColorsUV – VIS spectroscopy Jakub Kovář  Jiří Stančík

  2. Color and light • The starting point of an understanding of color is a description of light. • White light is actually made up of a whole range of colours, mixed together • We can see this if we pass white light through a glass prism

  3. Light spectrum • The colors produced by light passing through a prism are arranged in a precise array or spectrum from red through orange, yellow, green, blue, indigo and into violet • The intensity of light as a function of wavelength is called light spectrum

  4. Light spectrum • The visible spectrum of light is just a small part of the electromagnetic spectrum which extends from radio waves (long waves) to gamma rays (10-3 meters down to 10-15 meters, the size of the nucleus)

  5. The color of objects • Color is produced by the absorption of selected wavelengths of light by an object • The receptors of the human eye only respond to light in the visible spectrum

  6. Mixing of colors • RGB model uses red, green and blue color • CMYK model uses colors: cyan, magenta, yellow and black • Basic characteristics of colors are: hue, saturation, brightness

  7. UV – VIS spectroscopy • Analytical method • Light is a form of electromagnetic radiation • This radiation contains radio waves, visible light and X-rays • Light rays are composed of photons whose energy specifies a color from red to violet • A visible spectrum has many colors, and a rainbow is a typical spectrum

  8. Wavelenght of colors in UV – VIS spectrum • Visible region: 380 – 700 nm • Violet: 400 nm • Blue: 480 nm • Green: 500 • Yellow: 580 nm • Orange: 600 nm • Red: 700 nm

  9. Scheme of spectrophotometer

  10. Description of spectrophotometer • Source of radiation(tungsten lamp, laser …) • Monochrome (prism, graticule…) • Sample compartment(cuvette with sample) • Detector (diode-array detector)

  11. Principles of spectroscopy • Spectrometer exposes a chemical solution to the UV – VIS light across the electromagnetic spectrum from about 300 to 800 nm • A detector then measures the amount of light transmitted through the solution • The amount of light reached by the detector is then recorded as a spectrum

  12. Theory • Since UV-VIS spectroscopy is an absorption technique, Lambert - Beer's law can be applied • Spectrophotometer

  13. Vocabulary • Prism - krystal • Hue - odstín • Saturation - sytost • Brightness – světlost • Rain bow – dešťová poklona 

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