Synthetic fibres and plastics — Science STD 8 — Question

What is the difference between regular reflection and diffuse reflection of light? Name one object which can produce regular reflection of light and another which produces diffuse reflection of light.

Describe the threat to Taj Mahal monument due to air pollution.

What is meant by electroplating? What is the purpose of electroplating?

Give reasons for the following:
LPG is a better domestic fuel than wood.

What happens when a copper vessel is exposed to moist air for a long time?

Man, A has a defect of vision due to which he cannot see the nearby objects clearly (though he can see the distant objects clearly). On the other hand, man B has a defect of vision due to which he cannot see the distant object clearly (though he can see the nearby objects clearly). The defect in man A can be corrected by using spectacles containing lenses C whereas the defect in man B can be corrected by using spectacles containing lenses D.

1. Name the defect of vision in man (i) A, and (ii) B.
2. What type of lenses are (i) C, and (ii) D?

What is rayon? How is rayon made?

For electroplating copper on an iron object, which terminal of the battery (positive or negative) is connected to the iron object? Also name the electrolyte you will use for this purpose.

Define asexual reproduction. Name two methods of asexual reproduction in animals. Name two animals which reproduce by these asexual reproduction methods.

Give reason for the following:
Paper by itself catches fire easily whereas a piece of paper wrapped around an aluminium pipe does not.