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The Spec 20 Begins!. Sunlight is Electromagnetic Energy Light travels in wavelengths Wavelength: the distance from crest to crest Wavelength is measured in nanometers. Notice the difference in Wavelength. Why is the Ocean Blue?. Fig. 10-6. 1 m (10 9 nm). 10 –3 nm. 10 –5 nm.
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Sunlight is Electromagnetic Energy • Light travels in wavelengths • Wavelength: the distance from crest to crest • Wavelength is measured in nanometers
Fig. 10-6 1 m (109 nm) 10–3 nm 10–5 nm 103 nm 1 nm 106 nm 103m Micro- waves Radio waves Gamma rays X-rays UV Infrared Visible light 750 nm 500 600 700 550 650 380 450 Longer wavelength Shorter wavelength Higher energy Lower energy
Fig. 10-8 TECHNIQUE Refracting prism Chlorophyll solution Photoelectric tube White light Galvanometer 2 3 1 4 The high transmittance (low absorption) reading indicates that chlorophyll absorbs very little green light. Green light Slit moves to pass light of selected wavelength The low transmittance (high absorption) reading indicates that chlorophyll absorbs most blue light. Blue light
How does the Spec 20 work • The Spec 20 is used to measure the concentration of a solute in a solution • Compares the absorption and the transmittance • The higher the concentration, the higher the absorption and the lower transmittance
How do you work the Spec 20 • You must BLANK! • Blank is to eliminate the water from the solution.
What should the BLANK read? • ____ absorbance • ____ transmittance
Blank should read: • 0 absorbance and • 100% transmittance
What is the optimum wavelength? • optimum wavelength: wavelength of light the substance ABSORBS the MOST.
Measuring the Optimum Wavelength • Set machine to wavelength you want to test. • Blank the machine using water to eliminate the solvent. • Measure the absorbance and record.
Re-test for each Wavelength!! • Retest for each wavelength, increasing by 10 nm increments. • The optimum wavelength is the one with the greatest absorbance.
