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Experiment Colours of Light (Wavelength) absorbed by green plant

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NAME : Nur Amira Rozali TITLE : COLORS OF LIGHT (WAVELENGTH) ABSORBED BY GREEN PLANT DATE : 08/02/2011 INTRODUCTION Plant contains photosynthetic materials which are responsible in the photosynthesis processes. One of the materials is chloroplast. Chloroplast is actually an organelle found in plant cells and many other eukaryotic organisms. The chloroplast, in green plant, contains many pigments; a few of them are chlorophyll a and chlorophyll b, carotene and xanthophylls. All of these are natural pigments. Natural pigments1, are substances presence in animal and plant cell that produces color due to specific absorption of light and reflection of the unabsorbed light. In this experiment, the chlorophyll of the plant is going to be extracted and is centrifuged before it is tested with a set of calorimeter. Calorimeter is a device that is used to measure the absorption percentage of wavelength by a substance; in liquid state. RESEARCH QUESTION How does different green plant differ in the absorption of wavelengths? AIM To investigate the amount of absorption between two green plants (Spinach and Mustard) exposed to different range of wavelengths (440nm, 470nm, 490nm, 520nm, 550nm, 580nm, 590nm and 680nm). HYPOTHESIS The rate of absorption of between the two green plants (Mustard and spinach) is different. It is hypothesized that both spinach and mustard will have a large absorption of red and blue colour. Green is of an exception. It is also hypothesized that the mustard will have a lower absorption of green colour than that of spinach. Spinach has a greener color due to the existence of larger volume of chlorophyll than that that is available in the mustard. Hence it imposes a greener colour due to a higher reflection of green colour. VARIABLES Variables Method to control Range Independent Variable The wavelengths that are imparted on the green plant form a calorimeter Different wavelengths represents different colours are varied by using a calorimeter. ...read more.


This photosynthetic pigment is the one that reflects green colour. Two layers formed in the centrifuge tubes Two layers formed. The supernatant is at the top as it ahs a lower density than that of the debris below the centrifuge tube. Table 10: The table above shows the explanation. Graph 1: The percentage of absorption against wavelength of spinach sample Graph 2: The percentage of absorption against wavelength of mustard sample Graph 1 shows the graph of rate of photosynthesis od disk leaf against distance of the light source from the beaker. DISCUSSION a) The photosynthetic pigments are materials that are responsible for absorbing and trapping the light energy in the earlier steps of photosynthesis. One of the major pigments of photosynthetic materials is chlorophylls. Chlorophylls is a mixture of pigments that comprises of chlorophyll a, chlorophyll b and some carotenoids like B-carotene, Xantophyll and phaeophytin. However, other types of chlorophyll like chlorophyll c and bacteriochlorophyll are found in non green plant, protistans and photosyntehetic bacteria. b) The main objective of this experiment is to prove the fact that different form of plant which contains different concentration/number of photosynthetic pigments is tend to absorb different value of wavelength, hence, its different colour. Earlier hypothesis suggests that the wavelength will be absorbed by the photosynthetic pigment at a different absorption. Different wavelength which is absorbed or reflected by the photosynthetic pigments will determined the colour observed on the leaves. For example, two samples that are used in the experiment is spinach and mustard plant. In the earlier observation, it can be seen that the spinach plant is greener than that of mustard plant which a little bit light green. Hence a hypothesis is formed that the photosynthetic pigments in the spinach plant is able to absorb less amount of green wavelength compared to that of a mustard plant. Hence, more green wavelengths will be reflected by the pigments in spinach plant than that in mustard. ...read more.


(+0.01) Standard Solution Mustard sample T1 T2 T3 440 0.00 2.00 2.00 2.00 470 0.00 1.33 2.00 2.00 490 0.00 0.75 1.95 2.00 520 0.00 -0.30 1.44 1.87 550 0.00 0.58 1.55 1.88 580 0.00 -0.29 1.81 2.00 590 0.00 1.34 2.00 2.00 680 0.00 0.43 1.87 1.91 Wavelength (nm) Average percentage of absorbance of wavelength by mustard sample (With respect to standard solution at 0.00 absorbance) 440 [2.00+2.00+2.00]/3 = 2.00 470 [1.33+2.00+2.00]/3 = 1.80 490 [0.75+1.95+2.00]/3 = 1.60 520 [-0.30+1.44+1.87]/3 = 1.00 550 [0.58+1.55+1.88]/3 = 1.34 580 [-0.29+1.81+2.00]/3 = 1.17 590 [1.34+2.00+2.00]/3 = 1.78 680 [0.43+1.87+1.91]/3 = 1.40 Table 7: Average percentage of absorption by spinach sample (%) The calculation for the standard deviation for the average percentage of absorbance of wavelengths by both spinach and mustard samples (With respect to standard solution at 0.00 absorbance) is calculated by using the following formula: Standard deviation = Where, x: Percentage Absorbance of the samples (Spinach or mustard) exposed in different wavelengths Average percentage of absorbance of wavelengths by samples (Spinach or mustard) (with respect to standard solution at 0.00 absorbance) N: Number of trial Wavelength (nm) Average percentage absorbance of wavelength by spinach sample (With respect to standard solution at 0.00 absorbance) Standard deviation of the average percentage absorbance of wavelength 440 2.00 0.000 470 1.91 0.042 490 0.96 0.12 520 0.71 0.062 550 0.47 0.31 580 1.00 0.20 590 1.16 0.03 680 1.39 0.045 Table 8: The table above shows the standard deviation of the average percentage of absorption of wavelength of spinach Wavelength (nm) Average percentage absorbance of wavelength by mustard sample (With respect to standard solution at 0.00 absorbance) Standard deviation of the average percentage absorbance of wavelength 440 2.00 0.00 470 1.80 0.40 490 1.60 0.71 520 1.00 1.15 550 1.34 0.68 580 1.17 1.27 590 1.78 0.40 680 1.40 0.84 Table 9: The table above shows the standard deviation of the average percentage of absorption of wavelength of mustard. REFERENCE 1. Biology Oxford, Standard and Higher Level, Andrew Allot: Topic; Photosynthesis 2. Http://wikipedia_chlorophyll.com 3. Biology for IB Diploma, Hodder Education, CJ Clegg, page 288 ?? ?? ?? ?? ...read more.

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