Sources of Energy — Science STD 10 — Question

A diverging mirror of radius of curvature 40cm forms an image which is half the height of the object. Find the object and image positions.

Distinguish between a real and a virtual image of an object. What type of image is formed?

1. By a plane mirror.
2. On a cinema screen?

What are the two causes of speciation between two population?

Explain with the help of labelled ray-diagram, the defect of vision called hypermetropia, and how it is corrected by a lens.

On adding a drop of barium chloride solution to an aqueous solution of sodium sulphite, white precipitate is obtained.

1. Write a balanced chemical equation of the reaction involved.
2. What other name can be given to this precipitation reaction?
3. On adding dilute hydrochloric acid to the reaction mixture, white precipitate disappears. Why?

A pencil when dipped in water in a glass tumbler appears to be bent at the interface of air and water. Will the pencil to be bent to the same extent, if instead of water we use liquids like, kerosene or turpentine? Support your answer with reasons.

A person got his eyes tested by an optician. The prescription for the spectacle lenses to be made reads:
Left eye: +2.50D, Right eye: +2.00D

1. State whether these lenses are thicker in the middle or at the edges.
2. Which lens bends the light rays more strongly?
3. State whether these spectacle lenses will converge light rays or diverge light rays.

A combination of lenses for a camera contains two converging lenses of focal lengths 20cm and 40cm and a diverging lens of focal length 50cm. Find the power and focal length of the combination.

What is voluntary nervous system? Explain the working of voluntary nervous system with an example.

Name the scientist who gave the theory of origin of life on earth. What is this theory?