Control and Coordination — Science STD 10 — Question

A lens of focal length 20cm is used to produce a ten times magnified image of a film slide on a screen. How far must the slide be placed from the lens ?

What are the various factors which we should keep in mind while choosing a source of energy?

Why coal and petroleum are considered as air pollutants?

Describe the circulatory system in a fish.

Describe how sodium and chlorine atoms are changed into ions when they react with each other to form sodium chloride, NaCl. What is the name given to this type of bonding? (At. No of sodium = 11; At. No. of chlorine = 17)

The image of a candle flame placed at a distance of 30 cm from a mirror is formed on a screen placed in front of the mirror at a distance of 60 cm from its pole. What is the nature of the mirror? Find its focal length. If the height of the flame is 2.4 cm, find the height of its image. State whether the image formed is erect or inverted.

A magnifying lens has a focal length of 100mm. An object whose size is 16mm is placed at some distance from the lens so that an image is formed at a distance of 25cm in front of the lens.

1. What is the distance between the object and the lens?
2. Where should the object be placed if the image is to form at infinity?

Hydrogen has been used as a rocket fuel. Would you consider it a cleaner fuel than CNG? Why or why not?

Why does micelle formation take place when soap is added to water? Will a micelle be formed in other solvents like ethanol also?

How does a solenoid behave like a magnet? Can you determine the north and south poles of a current–carrying solenoid with the help of a bar magnet? Explain.