Our Environment — Science STD 10 — Question

A woman uses a device X made of a common metal for preventing pregnancy. This device works by preventing the implantation of fertilised egg cell (or embryo) in the female organ Y.

1. What are the two names of device X?
2. Name the organ Y.
3. Can this method of contraception protect a woman from acquiring a STD?

Why do stars seem higher than they actually are? Illustrate your answer with the help of a diagram.

In three test tubes A, B, and C, three different liquids namely, distilled water, underground water and distilled water in which a pinch of calcium sulphate is dissolved, respectively are taken. Equal amount of soap solution is added to each test tube and the contents are shaken. In which test tube will the length of the foam (lather) be longest? Justify your answer.

Give one example to show how the resistance depends on the nature of material of the conductor.

A doctor has prescribed a corrective lens of power, -1.5D. Find the focal length of the lens. Is the prescribed lens diverging or converging?

Give the pair of contrasting traits of the following characters in pea plant and mention which is dominant and recessive.

1. Yellow seed.
2. Round seed.

Explain why, a land plant may die if its roots remain water logged for a long time.

A person needs a lens of power, -5.5 dioptres for correcting his distant vision. For correcting his near vision, he needs a lens of power, +1.5 dioptres. What is the focal length of the lens required for correcting

1. Distant vision, and
2. Near vision?

Write the balanced chemical equations for the following reaction.
Sodium hydrogencarbonate on reaction with hydrochloric acid gives sodium chloride, water and liberates carbon dioxide.