Every day sciences 2007


Question no 1

a. Laser

Laser is a device which generates the coherent light or "well organised" light .Ordinary white light is made up of many different colours. Each colour has different wavelength and the photons of each colour are out of step with each other. In a beam of laser light, all the photon have the same wavelength and move in step , travelling along like a well drilled army. The mechanism relies on a process known as stimulated emission and the word laser is derived from light amplification by stimulated emission.
The essential components of a typical laser are

1. The active medium such as a ruby rod or carbon dioxide gas

2. A method of introducing energy into the active medium, for instance a flash lamp

3. A pair of mirrors is placed on each side of the active medium, one of which transmits part of the radiation that strikes it.

A typical laser using Ruby rod as an active medium has a pulse duration of 20 nsec. with power of 10 MW and the laser beam has a wave length of 694 nm.

b. Nuclear Reactor

A device in which the fission reaction involving neutrons and nuclear fuel is controlled for the production of heat is called "nuclear reactor". It is also known as " The nuclear power plant". This heat is converted by means of turbines and generator to electrical energy for commercial use. A nuclear power plant works in a similar way to an oil-fired or a coal-fired power station. The difference between the two types of power plants is in the fuel they use to heat the boiler. Inside a nuclear power plant, energy is released by nuclear fission in the core of a piece of equipment called the reactor. The energy heats water in the boiler ( the water boils and produce steam). This steam turns the huge turbine wheels, and the turbines drive the generator that produces the electricity.
There are three types of reactor which are given bellow.
1. Light water reactor (LWR)
2. Boiling water reactor (BWR)
3. Pressurised water reactor (PWR)
4. Heavy water reactor (HWR)
5. High-temperature Gas-Cooled reactor (HTGR)

Question no 2

a. Asteroids

Asteroids, also called minor planets or planetoids, are a class of astronomical objects.The asteroid is an small celestial bodies that drift in the solar system in orbit around the sun. between the orbits of mars and jupiter

b. Black Hole

black hole is an object with a gravitational field so powerful that even electromagnetic radiation(such as light) cannot escape its pull.

c. Aurora

The aurora is a bright glow observed in the night sky, usually in the polar zone. For this reason some scientists call it a "polar aurora" .

d. Sedimentary Rock

A Sedimentary rock is one of the three main rock groups (along with igneous and metamorphic rocks) . Sedimentary rocks cover 75% of the Earth's land area.Sedimentary rocks include common types such as chalk, limestone, sandstone and shale.

e. Epiphytes

An epiphyte is an organism that grows upon or attached to a living plant. Epiphytic plants are sometimes called "air plants" because they do not root in soil.

f. Ionosphere

The ionosphere is the part of the atmosphere that is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere.

Question no 4 (i)

1. Adrenal glands
2. thyroid glands

Question no 4 (ii)

a. Pancreas , stomach
b. thyroid gland
c. kidney
e. adrenal gland
f. Testes of male and overies of female

Question no 5a

There are nearly half a million species of plants on the earth. With the exception of few , all of them need three basic ingredients to survive : air , light and water . Plants are found in almost every type of habitat. They take their own food using simple raw materials and energy from the sun. Plants requires water to grow. They cannot get this water unless it is available in the soil. Plants obtain water from the soil through their roots. It then passes up the stem to the leaves and flowers. The plant does not take all the water available in the soil. Much of the remaining water evaporates into the surrounding air. The plants can be divided in to the following categories.

Non-Green Plants :

This is a group of plants having simple plant body without root, stem and leaves. They do not contain chlorophyll and hence do not involve photosynthesis. They can grow without the aid of sunlight and seem to popout of the ground overnight. Typical examples of nongreen plants are bacteria , fungi and viruses.

Green Plants :

These are those plants which contain chlorophyll and carry out photosynthesis. There are two categories of green plants : non-flowering and flowering plants.

a. Non-Flowering Plants (Cryptogams).

These are seedless green plants. They reproduce by means of spores. these plants have existed on earth for much longer than flowering plants. Many of them have remained almost unchanged for million of years. They generally have a simple structure and , with the exception of ferns , do not have supporting fiber.

b. Flowering Plants ( Phanerogams ).

These are seed containing green plants . There are two groups of seed plants : the gymnosperms and the angiosperms. This division is based on the type of seeds they have. The gymnosperms are the pine, fir , cedar , cypress and spruce three while the angiosperms include most other trees , the flowering plants, the grasses , crop plants , vegetable and weeds.


Question no 5 b

1. A vaccine is an antigenic preparation used to establish immunity to a disease

2. An antibiotic is a drug that kills or prevents the growth of bacteria

3. A solar eclipse occurs when the moon passes between earth and the sun

4. A reaction that releases energy in the form of heat is called exothermic

Question no 6

b. Mars is a barren desert. It is covered with red dust, that is why we call mars, the Red Planet.
c. Vitamin D increase the utilization of calcium and phosphorous of the body.
d.
e. Throat weakness causing the throat to close during sleep

NOte : Correct me in case of any mistake.

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