CBSE Guess > Papers > Question Papers > Class X > 2008 >Science > Science Theory

Ans.

1. The reaction will take place in test tube ‘A’.
2. CuSO₄ (aq) + Fe (s) - FeSO₄ (aq) + Cu (s) Iron is more reactive than Cu. Thus iron displaces copper from Copper Sulphate and forms FeSO4 and copper metal deposits on iron nail.
3. It is a displacement reaction.

Q. 13. Study the given diagram and answer the questions that follow it :

(i) Which defect of vision is represented in this case? Give reason for your answer.
(ii) What could be the two causes of this defect?
(iii) With the help of a diagram show how this defect can be corrected by the use of a suitable lens.

Sol.

1. In the given diagram, the defect of vision is Hypermetropia because in this defect of vision a person can not see the nearby objects clearly. as the image of nearby objects can not form on the retina but beyond the retina. Therefore this defect is also called far-sightedness.
2. Causes of Hypermetropia
   (a) due to low converging power of eye-lens (because of its large focal length)
   (b) due to eye-ball being too short.
3. This defect is corrected by using spectacles containing convex lenses.
   When a convex lens of suitable power is placed in front of the hypermetropic eye then the diverging rays of light coming from the nearby object are first converged by this convex lens. Due to this, the convex lens forms a virtual image of the nearby object at a point near to the hypermetropic eye. Then the hypermetropic eye can easily focus the image formed by convex lens on the retina.

Q.14. The position of three elements A, B and C in the Periodic Table are shown below :

Giving reasons, explain the following :
(a) Element A is a non-metal.
(b) Element B has a larger atomic size than element C.
(c) Element C has a valency of 1.

Science 2008 Question Papers Class X
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