Periodic Classification of Elements — Science STD 10 — Question

What is contraception? Name any two methods. How does the use of these methods have a direct effect on the health and prosperity of a family? State any three points.

Draw a diagram to show how a converging lens held close to the eye acts as a magnifying glass. Why is it usual to choose a lens of short focal length for this purpose rather than one of long focal length?

Mention the types of mirrors used as,

1. Rear view mirrors.
2. Shaving mirrors.

List two reasons to justify your answers in each case.

In the figure given alongside, a narrow beam of white light is shown to pass through a triangular glass prism. After passing through the prism, it produces a spectrum YX on the screen:
State the colour seen.

1. At X, and
2. At Y​​​​​​​​​​​​

​​​​​​​​​​​​

1. violet.
2. Red

2. ​​​​​​​Why do different colours of white light bend through different angles with respect to the incident beam of light?

We are advised to take iodised salt in our diet by doctors. Justify it's importance in our body.

What do you understand by the term “electromagnetic induction”? Explain with the help of a diagram.

What are the advantages of sexual reproduction over asexual reproduction?

What substances are contained in gastric juice? What are their functions?

State one example of a Dobereiner’s triad, showing in it that the atomic mass of middle element is half - way between those of the other two.

The non - metal A is an important constituent of our food and most of the fuels around us. A forms two oxides B and C. The oxide B is poisonous whereas oxide C causes global warming.

1. Identify A, B and C.
2. To which group of periodic table does A belong?
3. Name another element which is placed in the same group as A.