Visible and Ultraviolet Spectroscopy An obvious difference between certain compounds is their color In this respect the human eye is functioning as a spectrometer analyzing the light reflected from the surface of a solid or passing through a liquid Wavelength is defined on the left below as the distance between adjacent peaks(or troughs), and may be designated in meters centimeters or nanometers(10-9 meters ). Frequency is the number of wave cycles that travel past a fixed point per unit of time, and is usually given in cycles per second, or hertz(Hz) Visible wavelengths cover a range from approximately 400 to 800 nm
Visible and Ultraviolet Spectroscopy An obvious difference between certain compounds is their color. In this respect the human eye is functioning as a spectrometer analyzing the light reflected from the surface of a solid or passing through a liquid. Wavelength is defined on the left below, as the distance between adjacent peaks (or troughs), and may be designated in meters, centimeters or nanometers (10-9 meters). Frequency is the number of wave cycles that travel past a fixed point per unit of time, and is usually given in cycles per second, or hertz (Hz). Visible wavelengths cover a range from approximately 400 to 800 nm
DIspersion white Angle Light Red orange Yell Green Prism B n ed Violet
“ ROY G BIV wAvelength Amplitude Violet: 400-420 nm 420-440 Blue: 440-490 nm Green: 490-570 nm Higher Visible Spectrum L。wer Yellow 570-585nm Frequency Frequency ge:585-620 IR Red:620-780nm 400 500 60o 700800 Wavelength in nanometers
Violet: 400 - 420 nm Indigo: 420 - 440 nm Blue: 440 - 490 nm Green: 490 - 570 nm Yellow: 570 - 585 nm Orange: 585 - 620 nm Red: 620 - 780 nm “ROY G BIV
Color wheel 620nm 800 nm 580nm 400nm 560 nm 430nm 490nm Complementary colors are diametrically opposite each other Thus absorption of 420-430 nm light renders a substance yellow. and absorption of 500-520 nm light makes it red green is unique in that it can be created by absoption close to 400 nm as well as absorption near 800 nm
Complementary colors are diametrically opposite each other. Thus, absorption of 420-430 nm light renders a substance yellow, and absorption of 500-520 nm light makes it red. Green is unique in that it can be created by absoption close to 400 nm as well as absorption near 800 nm. Color wheel
Some Natural Organic Pigments OH o CH3 O H CO2H HO OH OH O Kermesic Acid (Carminic Acid Z=H from the insect coccus cacti Indigo from Isatis tinctoria (woad) Z=Br Punicin or Tyrian Purple from mollusks of the genus Murex Crocetin CH3 CH3 from saffron B-carotene from carrots extensively conjugated pi-electrons
“extensively conjugated pi-electrons