The retina of our eye has a large number of light- sensitive cells. There are two kinds of light- sensitive cells on retina: rods and cones. (1). Rods are the rod- shaped in the retina of an eye which are sensitive to dim light. Rods are the most important for vision in dim light (as du…

The light rays coming from the object kept in front of us enter through the cornea of the eye, pass through the pupil of the eye and fall on the eye- lens. The eye- lens, so it converges the light rays and produces a real and inverted image of the object on the retina. (Actually, the oute…

The main parts of the human eye are: Cornea, Iris, Pupil, Ciliary muscles, Eye lens, Ratena and Optic nerve. The eye -ball is approximately spherical in shape having a diameter of about 2.5 cm. We will now describe the construction and working of the eye. Construction of the Eye The fro…

The materials which are burnt to. Produce heat energy are known as fuels. Examples of fuels are: wood, Coal, Cooking gas (LPG), Kerosene, Diesel and Petrol. In our day life, the most important source of energy are fuels. Fuels are, in fact, the concentrated store- house of energy. This …

A biogas plant consists of a well shaped, underground tank T called digester, which is made of bricks, and has a dome- shaped roof D, also made of cement and bricks. The disgester is a kind of sealed tank in which there is no air (or oxygen).  The dome of the digester tank acts as a gas…