Absorbance Spectrum Lab Report

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Plotting the Absorption Spectrum of Lettuce Leaf Extract
November 14, 2012

Aim: To see how chlorophyll pigments absorb electromagnetic radiation at different wavelengths, with the use of a spectrophotometer to vary the wavelength of incident light, and then plot an absorption spectrum.

Hypothesis: The chlorophyll pigments of the spinach leaf's chlorophyll extract will absorb more electromagnetic radiation at wavelengths which correspond to the wavelengths of colors other than green, as chlorophyll is green and it will reflect green light.

Collection of Raw Data

Beaker | 50mL beaker, same for each group |
Filter paper | Semi-transparent, thin |
Spinach leaves | 5 identical dark green leaves |
Ethanol | Colorless and transparent; looks just like water. | Chlorophyll extract | Green; became greener as more chlorophyll was released from the leaf tissue. | Adjusted extract | The more ethanol we added to the extract, the less green it became. | Heater | Hot plate, same for each group |

Heating process | Bubble formation was observed as the leafs were being heated. | Table 1.1: Qualitative Data

Wavelength of Incident Light (nm)
| 400 | 440 | 480 | 520 | 560 | 600 | 640 | 680 | 700 | Relative Absorbance (±0.005nm)
Group 1 | 0.09 | 0.11 | 0.04 | 0.01 | 0.01 | 0.01 | 0.03 | 0.03 | 0.01 | Group 2 | 0.14 | 0.15 | 0.07 | 0.02 | 0.02 | 0.02 | 0.04 | 0.04 | 0.01 | Group 3 | 0.11 | 0.13 | 0.09 | 0.05 | 0.04 | 0.02 | 0.04 | 0.02 | 0.03 | Group 4 | 0.12 | 0.14 | 0.07 | 0.01 | 0.01 | 0.01 | 0.02 | 0.03 | 0.01 | Table 1.2: The rate of absorbance of chlorophyll pigments at different wavelengths.

Processing Raw Data

Wavelength of Incident Light (nm) | The Average Absorbance...
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