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:

(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.

In the preparation of soap, sodium chloride causes:

Select from the following salts which may be used to prepare hard water required for the experiment.

A. CaSO₄

B. Na₂SO₄

C. CaCl₂

D. K₂SO₄

E. NaHCO₃

F. MgCl₂

Four students A, B, C and D did their experiment of finding the focal length of convex lens by obtaining image of a distant object as follows:

• Student A used the window grill in the laboratory as the object and a white paper sheet held in hand as the screen.

• Student B used a distant tree in the shade and a white thick held in a stand as the screen.

• Student C used a well illuminated laboratory window grill as the object and a white paper sheet held in a stand as the screen.

• Student D used a well illuminated distant tree as the object and a white thick board held in a stand as the screen.

Which student has used the correct method for performing experiment out of the above setups?