Light Intensity Essay

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In the light intensity experiment, tubes of buffer solution, chloroplast, water and DPIP were placed in different intensities of light to determine how light intensity affects the reaction rate of photosynthesis. The reaction rate was measured by absorbance values in five-minute increments for 30 minutes. The tubes were placed at 24 cm away, 30 cm away, 49 cm away, and completely dark. The tube that was closest to the light had the smallest absorbance value, while the dark tube had the highest value. As the light intensity increases, the absorbance value decreased. In the action spectrum experiment, 10 aspirated spinach leaves and sodium bicarbonate solution were mixed together in beakers then each beaker was placed in different light boxes.
The rate of photosynthesis can be determined indirectly by DPIP, which is a dye that essentially mimics coenzyme NADP, which becomes reduced when an electron is added to NADPH during light reactions (Lab manual, pg.114). When reduced the solution changes from blue to clear. When DPIP becomes clear, photosynthesis has occurred. Light Intensity can alter the photosynthetic rate of chloroplasts. At low light intensity, photosynthesis occurs at a slower rate due to the fact that only a small quantity of ATP is created(Slitcher). As light intensity increases, larger amounts of ATP and NADPH are created, increasing the rate of photosynthesis. Photosynthesis also requires a specific wavelength for the pigments in chloroplast to absorb it. Different pigments tend to absorb different wavelengths of visible light. Since pigments can only absorb certain wavelengths, the others are transmitted or reflected. The activity of photosynthetic pigments allows us to predict which pigments are responsible for photosynthesis at specific wavelengths. The purposes of our experiments were to observe whether or not light intensity and wavelength affect the rate of photosynthesis as well as find out what pigments were active at what point of
In our light intensity experiment our hypothesis was supported. The effect of light intensity is proportional to the photosynthetic rate. The absorbance values on the other hand had an inverse relationship to photosynthetic rate. Plants have pigments that pick up certain wavelengths of light. The pigment in the plant determines what wavelengths of light can be absorbed. Plants that are green normally contain chlorophyll a as well as b. These chlorophylls, absorb different types of wavelengths, but don 't absorb ones that are green. These plants are green because that wavelength of light is reflected instead of absorbed. Different colors of light can affect how much photosynthesis occurs, because only certain colors are absorbed. The more color that’s absorbed, the more light that’s absorbed, which leads to more photosynthesis. Our experiment demonstrated that the red wavelength was the most effective for photosynthesis behind white, which was our positive control due to the fact that it contains all the colors of the spectrum. In our final experiment for the absorption spectrum our results supported our hypothesis and the absorbance levels decreased as we increased the

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