Photosynthesis occurs in chloroplasts．Students investigated the effect of light intensity on the rate of photosynthesis in a chloroplast suspension． The blue dye DCPIP can be used to investigate photosynthesis．During photosynthesis，the dark－blue colour of the DCPIP changes and gradually disappears so that it becomes colourless． A chloroplast suspension that is made from spinach leaves has a green colour． The students used this method： Step 1 Prepare a chloroplast suspension from fresh spinach leaves． Step 2 Label one test－tube $$\(\mathbf{A}\)$$ and another test－tube $$\(\mathbf{B}\)$$ ． Step 3 Put $$\(1 \mathrm{~cm}^{3}\)$$ of the green chloroplast suspension into test－tube $$\(\mathbf{A}\)$$ and into test－tube $$\(\mathbf{B}\)$$ ． Step 4 Put test－tubes $$\(\mathbf{A}\)$$ and $$\(\mathbf{B}\)$$ into an ice－cold water－bath for two minutes． Step 5 Put $$\(5 \mathrm{~cm}^{3}\)$$ of the blue DCPIP solution into test－tube A．Put a test－tube rack 10 cm from a bright light．Put test－tube $$\(\mathbf{A}\)$$ into the test－tube rack． Step 6 Turn on the light and start the stop－clock． Step 7 Measure the time taken for the blue liquid in test－tube $$\(\mathbf{A}\)$$ to return to a green colour． Step 8 Reset the stop－clock to zero． Step 9 Move the test－tube rack so that it is 30 cm from the bright light． Step 10 Put $$\(5 \mathrm{~cm}^{3}\)$$ of the blue DCPIP solution into test－tube B． Put test－tube B into the test－tube rack and start the stop－clock． Step 11 Measure the time taken for the blue liquid in test－tube $$\(\mathbf{B}\)$$ to return to a green colour． The times measured in step 7 and step 11 are shown in Fig．1．1． time recorded for test－tube $$\(\mathbf{A}\)$$ time recorded for test－tube B Fig． 1.1 * 0000800000003 * （c）Fig． 1.2 is a photograph of a seed from a dandelion plant，Taraxacum officinale． Fig． 1.2 (i) Draw a large diagram of the whole dandelion seed shown in Fig. 1.2. (ii) Line $$\(\mathbf{P Q}\)$$ in Fig. 1.2 represents the length of the achene of the dandelion seed. Measure the length of line $$\(P Q\)$$ in Fig. 1.2. length of $$\(P \mathbf{Q}\)$$ ........................................... mm Calculate the actual length of the achene, using the formula and your measurement. $$\[ \text { magnification }=\frac{\text { length of line } P Q \text { in Fig. } 1.2}{\text { actual length of the achene }} \]$$ Give your answer to two significant figures. Space for working. ..................................................... . mm

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