PART - 2 CH - 7 How do Organisms Reproduce ? — Science STD 10 — Question

What could be the reasons for adopting contraceptive methods?

A person with a myopic eye cannot see objects beyond 1.2 m distinctly. What should be the type of the corrective lens used to restore proper vision?

What is the role of acid in stomach ? 

An object, 4.0 cm in size, is placed at 25.0 cm in front of a concave mirror of focal length 15.0 cm. At what distance from the mirror should a screen be placed in order to obtain a sharp image? Find the nature and the size of the image.

What are the functions of the acid in our stomach?

A convex lens forms a real and inverted image of a needle at a distance of 50 cm from it. Where is the needle placed in front of the convex lens if the image is equal to the size of the object? Also, find the power of the lens.

Blue crystals of copper sulphate on heating in a dry test tube become colourless. Why?

What is meant by saturated and unsaturated carbon compounds?

What happens, when ammonium chloride is added to barium hydroxide ? What changes in temperature take place during the reaction?