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Question
Describe an experiment to prove that sunlight is necessary for photosynthesis.
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Solution
Experiment to prove that sunlight is necessary for photosynthesis:
a. A potted plant is kept in the dark for two days to destarch the leaves.
b. A part of a leaf is covered with a black paper by clip.
c. Now the plant is kept in the light for few hours.
d. The leaf is plucked and is boiled in water and is then decolourized with
alcohol.
e. The portion of leaf which received light turns blue with iodine because
photosynthesis took place in that part of leaf.
f. The part of leaf which was covered with black paper remains colourless
because photosynthesis could not take place in the absence of sunlight.

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RELATED QUESTIONS
A potted plant was taken in order to prove a factor necessary for photosynthesis. The potted plant was kept in the dark for 24 hours. One of the leaves was covered with black paper in the centre. The potted plant was then placed in sunlight for a few hours.
(i) What aspect of photosynthesis was being tested?
(ii) Why was the plant placed in the dark before beginning the experiment?
(iii) During the starch test, why was the leaf
(1) boiled in water
(2) boiled in methylated spirit
(iv) Write a balanced chemical equation to represent the process of photosynthesis.
(v) Draw a neat diagram of a chloroplast and label its parts.
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The figure given below is for performing an experiment on photosynthesis.

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(iii) What do you conclude from this experiment?
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