Modulation:Modulation is nothing but, a carrier signal that varies in accordance with the message signal. Modulation technique is used to change the signal characteristics. Basically, the modulation is of following two types: 

  1.Analog Modulation

  2.Digital Modulation

It is a type of government or political system ruled by citizens, people who are members of a society. In a democracy, citizens hold some level of power and authority, and they participate actively in the political, or decision-making, process of their government.

Part of human boday which helpa us to look things arouns us

A general scarcity of basic necessities of life is called poverty.

The basic necessities include food, shelter, clothing, healthcare, sanitation, etc.

Some of the issues which are related to poverty are; Landlessness, Unemployment, Size of families, Illiteracy, Poor health/malnutrition, Child labour and Helplessness.

An ecosystem is a community of living organisms in conjunction with the nonliving components of their environment (things like air, water and mineral soil), interacting as a system.

The horizontal rows in the long form periodic table are called periods. There are 7 periods.

1) The number of main shells present in the atom of particular element decides to which period it belongs to. Eg : i) Hydrogen (H) and Helium (He) atoms contain only one main shell (K). Therefore they belongs to period - 1. ii)The elements Li, Be, B, C, N, O, F and Ne contain two main shells (K and L) in their atoms. Therefore they belong to period - 2.

2) The number of elements in a period depends on how electrons are filled into various shells. Each period starts with a new shell and ends when shell is filled with respect to the 's' and 'p' levels of its main shell. The first period contains two elements because the K shell contains only one sub-shell i.e., Is, which can accommodate 2 electrons only.

3) The second period starts with the 2nd main shell (L), which has two sub shells 2s and 2p, which can accommodate 8(2 + 6) electrons. Hence second period contains 8 elements.

4) Third period starts with third main shell (M), which has 3 sub-shells 3s, 3p and 3d, but while electrons are being filled into the shell. '3d' gets electrons only after '4s' is filled. Therefore the 3rd period contains again 8 elements by filling 3 s and 3p.

5) Fourth main shell (N) has four sub-shells, 4s, 4p, 4d and 4f but while filling electrons, they are filled in the order 4s, 3d and 4p. Due to this, 4th period contains 18 elements (2 + 10 + 6).

6) Similarly 5th period contains 18 elements, 6th period contains 32 elements.

7) 7th period is incomplete and contains 3 elements from s-block 14 elements from (f-block, 10 elements from d-block, some elements from p-block).

8) The 4f elements (Lanthanoids) and 5f elements (Actinoids) are shown separately at the bottom of the periodic table.