The lights are essential for photosynthesis and it plays a major role. All the food we eat and all the fossil fuel we use is a product of photosynthesis, which is the process that converts energy in sunlight to chemical forms of energy that can be used by biological systems. Photosynthesis is carried out by many different organisms but usually by plants and algae. All these organisms convert CO2 (carbon dioxide) to organic material by reducing this gas to carbohydrates in a rather complex set of reactions.

Electrons for this reduction reaction ultimately come from water, which is then converted to oxygen and protons. Energy for this process is provided by light, which is absorbed by pigments. Chlorophylls absorb blue and red light and carotenoids absorb blue-green light but green and yellow light are not effectively absorbed by photosynthetic pigments in plants; therefore, light of these colors is either reflected by leaves or passes through the leaves(Arizona 2007). This is why plants are green. A certain colors of light such as red and blue colors of light absorbed by the plant are more effective in driving photosynthesis than other colors of light.

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The wavelengths of blue (400-500) nm and red (600-700 nm) lights are the most effective and yellow and green (500-575 nm) are least effective in driving photosynthesis (Campbell). Red and blue are expected to be most advantageous for photosynthesis. The purpose of our experiment is to investigate how the wavelength of a light affects photosynthesis. We also measured how intensity of the light can affect the rate of photosynthesis. The experiment variables are intensity and color of a light and everything else such as amount of chlorophyll extract was controlled. Our hypothesis the rate of photosynthesis is lower in yellow light than white light which contains both blue and red lights in visible spectrum and stronger the light intensity, the rate of photosynthesis increases.


4 test tubes that each contained chloroplast extracts with the mixture of water and 0.2mM DCPIP dye were placed at three different distances from the light source. 3 test tubes were place directly in front of the light source and one test tube was placed into a dark plastic. The value of absorbance was recorded every 2 minutes by spectrometers for every test tube. Light intensity was also measured from initial and final of the experiment.


There are four main photosynthetic pigments found in the chloroplast. They are chlorophyll 1, chlorophyll b, xanthophylls, and carotenes (Table 1). All these pigments absorb light and use the light energy in photosynthesis. An initial experiment showed the distance of which pigments traveled across the chromatography paper. The highest distance observed was pigment Xanthophylls and lowest was chlorophyll1. This distance indicates the ability of absorption. Further the distance pigments traveled higher ability to absorb lights.