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# Photosynthesis and Light intensity

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Introduction

PLANNING A Aim: The aim of this experiment is to investigate the effect of different light intensities on the rate of photosynthesis Theory & Hypothesis: The photosynthesis rate is often measured by the amount of carbon dioxide absorbed or oxygen evolved by a plant. With increase in light intensity, photosynthesis begins, and some carbon dioxide from respiration is utilized in photosynthesis. As light intensity increases, there is an increase in the rate of photosynthesis, and this light intensity can be increased or decreased by bringing the source of light closer to or further away from the plant. Hypothesis: Hence, we can predict that with increase in light intensity, the rate of photosynthesis would also increase. Variables: The variables in the experiment are light intensity and the rate of photosynthesis. ...read more.

Middle

8. Ruler 9. Stop-watch Procedure: 1. Place the hydrilla in a test-tube filled with dilute sodium hydrogen carbonate solution 2. Fix the test-tube on the retort stand 3. Placed the lamp at a distance of about 5cm from the test-tube 4. Start the stop-watch 5. Start counting the number of bubbles produced 6. Note the number of bubbles produced after 2 minutes in a table 7. Repeat the above steps with the lamp at distances of 10cm, 15cm, 20cm and 25cm Data Collection (Observation): No. Distance between lamp and plant/cm No. of bubbles/2 minutes 1 5 150 2 10 124 3 15 103 4 20 90 5 25 55 Discussion: Thsu the above observations are according to our hypothesis. ...read more.

Conclusion

Thus at a close intensity of 5 cm, maximum number of bubbles is formed, and at the least intensity of 25 cm, least number of bubbles is formed. Modification: 1. Use other types of plants. 2. Conduct the experiment various times ,in order to ensure accurate results. Precaution 1. Start counting time only from the first bubble. 2. Ensure that the light intensity is not too high, because otherwise the hydrilla may die Limitation: 1. The experiment was carried out once, and thus the result may be inaccurate Conclusion: Hence, we can conclude that light intensity is directly proportional to the rate of photosynthesis, and greater light intensity produces more bubbles. ...read more.

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