colors uv – vis spectroscopy jakub kovář jiří stančík
TRANSCRIPT
ColorsUV – 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
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
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)
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
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
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
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
Scheme of spectrophotometer
Description of spectrophotometer
Source of radiation(tungsten lamp, laser …)
Monochrome (prism, graticule…) Sample compartment(cuvette with
sample) Detector (diode-array detector)
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
Theory Since UV-VIS
spectroscopy is an absorption technique, Lambert - Beer's law can be applied
Spectrophotometer lcA
0log
Absorpční spektrum benzenu
0
0,5
1
1,5
2
2,5
3
200 220 240 260 280 300 320 340 360
(nm)
A
plynný kapalný
Vocabulary
Prism - krystal Hue - odstín Saturation - sytost Brightness – světlost Rain bow – dešťová poklona