P-1 Metallurgy — Science STD 10 — Question

Ciliary muscles of human eye can contract or relax. How does it help in the normal functioning
of the eye?

Explain how, harmful ultraviolet radiations of sunlight are prevented from reaching the earth’s surface.

On going through the modern periodic table it is seen that the elements Li, Be, B, C, N, O, F and Ne belong to the period-2. write down electronic configuration of all or them.

Amphibia and Reptilia.

Explain with a suitable diagram, how a concave mirror converges a parallel beam of light rays. Mark clearly the pole, focus and centre of curvature of concave mirror in this diagram.

Two electric bulbs rated 60 W and 40 W respectively are used 5 hours per day for 20 days. If the cost of a unit is ₹ 4.00, find the cost of the energy used.

Give a method for the disposal of household wastes such as left-over food, fruit and vegetable peels, and leaves of potted plants.

Explain the following in terms of gain or loss of oxygen with one example:

1. Oxidation.
2. Reduction.

Explain why, ethene decolourises bromine water whereas ethane does not.

Give the general formula of an:

1. Alkane.
2. Alkene.
3. Alkyne.