What is a Telescope ?

  

     A Telescope is a device that is used to observe far objects (or) bodies in the night sky such as Stars, Planets, and Galaxies. At the medieval ages, these are used to see near and distant objects both on and off the earth. These devices are used to find many exo-planets that exist far beyond some light years away from earth. Since Universe is evolving at an enormous rate, It is even sometimes difficult to these telescopes to locate celestial bodies that exist very far in deep space. These with some special abilities such as x-ray and gamma-ray vision these devices may be able to see bodies that actually difficult to capture in our infinite universe.

What is a Thermometer ?

     A thermometer is an instrument that is used to measure the temperature of a body. To measure the temperature of the body, Thermometer should be in direct contact with the body. When the Thermometer is subjected to high temperature, The Mercury will expand linearly inside the thermometer. If the Thermometer contact is broke with the body, The Mercury will regain its original position. Here raising the temperature is directly proportional to the linear variation of Mercury in the Thermometer. Mercury is the only element that is in the form of liquid at room temperature. It has a high coefficient of expansion i.e., even a slight change in temperature can be measured. Mercury has a high boiling point(356.7 ^O C) so high temperatures can also be measured.

Why do the Pressure Cookers are used on Mountains?

     When we go to high altitudes, the pressure decreases. As the pressure decreases, the boiling point also decreases and latent heat of vaporization increases. Latent heat means that the heat associated with the phase change of a substance. For example

• 0 degree centigrade of Ice to 0 degree centigrade of Water.
• 100 degree centigrade of Water changes to 100 degree centigrade of Steam.  

     Due to low pressure the boiling point is low and have latent heat of vaporization increases . At high altitudes, We use pressure cookers which is helpful to cook our food at a normal temperature like the temperature which is used to cook the food at low altitudes.

     If we use normal pots to cook food the temperature of the water increases at a high rate due to low pressure but to cook our food latent heat is required. To acquire that latent heat more heat supply is required and it takes more time to reach the latent heat. It's becoming more expensive in this manner to cook food at high altitudes. So for cost effective cooking, we use pressure cookers on Mountains.

Why does Railway Tracks expand and contract during temperature change ?

     Generally Rails are made up of steel. When steel is subjected to high temperature it expands but does not changes its shape. In solids atoms are very closely packed and when the solid is subjected to high temperature the molecules starts vibrating and the gap between the molecules increases so there will be expansion in the material. When the temperature starts decreasing, The molecules in the material starts getting close to each other so the material contracts. During Summer, the rails are subjected to high temperature and expands longitudinally but not laterally in the Winter the contracts due to low temperatures. These rails even expands and contracts during Day and Night regularly. The gap is maintained between the rails to expand freely. If this gap is not maintained the expansion is restricted and rails get bends. Due to this phenomenon, These bends may lead to accidents.