Authors : Janchai Yingprayoon, Isika Rodcharoen and Wiraya Soonsim
Page Nos : 76-81
Description :
A simple spectroscope is constructed using a transparent CD Rom as a diffraction grating for dispersion of light. Red laser (wavelength 650 nm), green laser (wavelength 532 nm) and blue laser (wavelength 445 nm) are used as reference wavelengths on a spectrum scale. A super bright white light LED was used as a light source for the measurement of a spectrum. A digital camera was used to take a picture of an absorption spectrum. Chlorophyll solution was extracted from green leaves using methyl alcohol. Haemoglobin dilute solution from human blood was also prepared for the measurement of an absorption spectrum. Reference absorption spectra of some samples are compared with the results from this simple spectrometer, showing similar results. Chlorophyll and Hemoglobin absorb different bands of light in the spectrum, and it seems that they are complement each other to complete white light spectrum. However, both Chlorophyll and Hemoglobin have high absorption around 400-450 nm which is in the range of blue color. Chlorophyll absorbs blue laser light and emits red light by fluorescence. Using a UV light source shining into chlorophyll solution, we can see red color from chlorophyll solution and a red leaf. This is because of fluorescence of chlorophyll when absorbing UV light.
