Q.12 Explain Electromagnetic radiation.
Ans. Electromagnetic radiation is a self propagating wave it consist of the energy in terms of photons. Photons can have different frequencies. The energy associated with a particular radiation depends upon its wavelength.
Types of radiation:-
[a] Alpha particles has a positive electric charge. They have a large specific ionization values. These particles can cause health hazard through inhalation; because they can not penetrate outer layers of skin.
[b] Beta particles are light in weight, and are penetrative. These cause internal or external health hazard due to ionization radiation.
[c] X-rays and gamma rays are very penetrating compared to alpha and beta particles. They constitute the chief health hazard.
Q.13 Write short notes on conventional and non-conventional sources.
Ans. Conventional And Non-Conventional Sources: -
Coal, oil and gas are commonly known as conventional energy resources. Conventional (also known as commercial resources) resources is limited due to their insufficient availability. Therefore, a large amount of energy can be derived from non-commercial resources like agricultural waste, firewood, solar, wind etc. These resources are known as non-conventional energy resources. Conventional energy resources are used conventionally and can be stored. The non-conventional energy resources can not be easily stored.
Q.14 Describe hydro-electric, nuclear and solar sources.
Ans. Hydro-Electric Sources: -
A hydro-electric power plant harnesses power from water flowing under pressure (i.e., water falling from a height). Electric generators driven by water turbines represent the use of water energy as electricity.
Hydro-power is not only a clean, non-polluting source of energy; but also a most conventional renewable energy source. Further, with the limited sources of coal, lignite and oil, growing reliance would have to be placed on hydel power. Except for the heavy initial investment, hydel projects have a definite edge over other power plants. Hydro or hydel power is one of the most important sources of energy, next only to thermal power. This can be assessed by the fact that nearly 30%of the total power of the world is met by hydro-electric power. The total hydro potential of the world is about 5,000 GW.
Nuclear Sources: -
The sources of radioactivity (nuclear) are both natural and man-made. The natural sources include:
(i) Cosmic rays from outer space. The quantity depends on altitude and latitude, it is more at higher latitudes and high altitudes.
(ii) Emissions from radioactive materials from the Earth’s crust.
People have been exposed to low levels of radiation from these natural sources for several millenia. But it is the man-made sources which are posing a threat to mankind. The man-made sources of radioactivity are nuclear wastes (i.e. waste material that contains radioactive nuclei) produced during the:
(i) Mining and processing of radioactive ores;
(ii) Use of radioactive material in nuclear power plants;
(iii) Use of radioactive isotopes in medical, industrial and research applications; and
(iv) Use of radioactive materials in nuclear weapons.
The greatest exposure to human beings comes from the diagnostic use of X-rays, radioactive isotopes used as tracers and treatment of cancer and other ailments.
Solar Sources: -
We receive from the Sun a pure, non-polluting, and inexhaustible form of energy. Solar energy comes from the thermonuclear fusion reaction constantly taking place in the Sun.
An enormous amount of solar energy falls on this tiny planet Earth. What we get from the Sun in one month is more than the energy stored in all the fossil fuels we have. Also, using this vast amount of energy does not pollute the biosphere in any way.
There is also some bad news: solar energy is a diffuse source falling evenly over a vast area and the first problem is collecting it efficiently. The second problem is converting it into a usable form such as electricity.
You can guess what the third problem is: What do we do when it is cloudy and the Sun does not shine? We must have an efficient way of storing the energy. All research in solar energy is about finding cost-effective ways of collection, conversion, and storage.
