Force and pressure. — Science STD 8 — Question

Name the part of the eye:

1. Which controls the amount of light entering the eye.
2. Which converges light rays to form the image.
3. On which image is formed.
4. Which carries the image to brain.
5. Which changes the curvature (or thickness) of eye-lens to focus objects lying at various distances.

Raj Kumar and his wife Sunita have been blessed with a baby girl. On the other hand, Kripa Shanker and his wife Vimla have been blessed with a baby boy. What type of sex chromosome has been contributed:

1. By raj Kumar.
2. By Sunita.
3. By Kirpa Shanker.
4. By Vimla.

What is meant by ‘Species’? Give any five examples of species.

Give five example each of animals which develop:

1. Inside the mother.
2. Inside eggs which the mother lays.

The material A is a fossil fuel which is extracted from the earth. It is said to be formed from the buried, large land plants by a very slow process B. When A is heated in the absence of air in a process called C, then it gives three products D, E and F. The product D is used as a reducing agent in the extraction of metals, the product E is used as an industrial fuel whereas the product F has been traditionally used for metalling the roads.

1. What could material A be?
2. What is (i) physical state, and (ii) colour, of A?
3. Name the processes (i) B, and (ii) C.
4. What are (i) D, (ii) E, and (iii) F?

Describe menstrual cycle. What is the duration of menstruation cycle in women?

State the various ways of preventing the occurrence and spreading of communicable diseases.

Explain with the help of diagrams, how the use of oil reduces friction between two surfaces in contact with each other.

State one use each of the following products of petroleum:

1. Petroleum gas
2. Petrol
3. Diesel
4. Lubricating oil
5. Bitumen

The species P and Q of wild animals are found only in a ‘particular area’. The species R of wild animals is listed in Red data book of India whereas species S of wild animals no longer exists anywhere on the earth.

1. What name is given to species like P and Q?
2. What are the species like R known as?
3. Name one species like R?
4. What is the special name of species like S?
5. Name one species like S?