Q24 of 38 Page 1

(i) Rohit claims to have obtained an image twice the size of object with a concave lens. Is he correct? Give reason for your answer.

(ii) Where should an object be placed in case of a convex lens to form an image of same size as of the object? Show with the help of ray diagram the position and the nature of the image formed.


(iii) With the help of ray diagram, illustrate the change in position, nature and size of the image formed if the convex lens in case of (ii) is replaced by concave lens of same focal length.

(i) No, as a concave lens always form a diminished image of an object.


(ii) At centre of curvature of convex lens i.e. 2f


Image formed will be real, inverted, same size as object



(iii) Image will be virtual, diminished, erect and formed between focus and optical centre of concave lens.



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22

What is the difference in colours of the sun observed during sunrise/sunset and noon? Give explanation for each.

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(i) Which property of concave mirror is utilized for using them as shaving mirrors?

(ii) Light passes through a rectangular glass slab and through a triangular glass prism. Using proper ray diagram, explain in what way does the direction of the two emergent beams differs with respect to the incident beam of light.


(iii) A concave lens has a focal length of 50 cm Calculate its power.

 25

In the preparation of soap, sodium chloride causes:

 26

Vishakha carried out saponification reaction in the lab and she gave following comments as:

(i) Soap is salt of fatty acid.


(ii) Heat is absorbed in this reaction.


(iii) Reaction mixture is basic in nature


(iv) These are neutralization reaction


The correct statements are: