Photosynthesis Lab

Photosynthesis Lab

Data Collection:

The absorption of different wavelengths of light by Chlorophyll

Wavelength (nm) Absorbance of light by chlorophyll

(Arbitrary units) Diluted Calculation New Reading

(Arbitrary units)

Violet 430 2.35 50% 2.35 x 2 3.20

Blue 470 1.09 - - 1.09

Blue-Green 492 0.38 - - 0.38

Green 520 0.77 - - 0.77

Yellow-Green 550 0.85 - - 0.85

Yellow 580 1.43 - - 1.43

Orange 600 0.65 - - 0.65

Red 700 0.16 - - 0.16

Absorption and reflection of light: Different substances absorb different wavelengths of light in differing amounts. If an object absorbs all the wavelengths of visible light and reflects light in the green part of the spectrum we will see the object as green. If all the wavelengths of visible light are absorbed the object appears black, and if they are all reflected it appears white.

Data Processing:

Graph 1: Absorption of light by chlorophyll

Conclusion and Evaluation:

Graph 2 Graph 3

Comparing my experimental “absorption of light by chlorophyll” (graph 1) to the above existing graphs (graph 2 and 3), I can notice that they are relatively similar. Very little absorption occurs in the “green” region of the spectrum in both graphs 1 and 2. Graph 2 shows two peaks, one in the violet region (chlorophyll a) and one in the yellow-orange region at around the wavelength 670 nm. Due to the limitations of the colorimeter and its incapability of recording light absorbed by chlorophyll in between wavelengths of 600-700 nm, we did not have a recording for this region and thus no peak is shown. Also, in graph 1 , there is more absoption of yellow light while in graph 2 there I almost none, this can be due to the possibly of chlorophyll used from different plants. The least absorption (graph 1) is in the ‘blue-green’ region, proving the leaves we used were dark green color.

Chlorophyll does not absorb all the wavelengths of visible light equally. Chlorophyll a, the most important light-absorbing pigment in plants, does not absorb light in the green part of the spectrum. Light in this range of wavelengths is reflected. This is the reason why chlorophyll is green. My experimental graph 1 also shows a peak at 430 nm and the existing graph 2 (chlorophyll a) also peaks around