Basic Concepts of Sets

1. Sets

What is pay-in-Slip

 Pay-in-Slip : Pay-in-Slip is a document used to deposit cash or cheque into the Bank. Pay-in-Slip serves the purpose of providing an evidence that on a particular date a specific amount (or cheque) has been deposited in the Bank.

LED(Light-emitting Diode)

Filiform of LED are Light-emitting Diode. 

 When a conduction electron makes a transition to the valence band to fill up a hole in a p-n junction, the extra may be emitted as a photon. If the wavelength of this photon is in the visible range (380mm - 780mm), one can see the emitted light. Such a p-n junction is known as light-emitting diode abbreviated as LED. For silicon or germanium, the wavelength falls in the infrared region. LEDs may be made from semiconducting compounds like gallium such as, arsenide of indium phosphide. LEDs are very commonly used in electronic gadgets as indicator lights.

BROWNIAN MOTION

 we have assumed in kinetic theory of gases that the molecules of a gas are in constant random motion, colliding with each other and with the walls of the container. This is also valid for a liquid. Robert Brown, a botanist, accidentally came across an evidence of this type of molecular motion in 1827. He was observing small pollen grains suspended in water, under a powerful microscope. He observed that although the water appeared to be at complete rest, the grains were moving randomly in the water, occasionally changing their directions of motion. The molecules strike the particles of the pollen grains and kick them to move in a direction. Another collision with some other molecules changes the direction of the grain.

The molecules are too small to be directly seen under a normal microscope, but the grains can be seen. A piece of wood floating in water can be seen with naked eyes but its mass is so large that it does not respond quickly to the molecular collisions. Hence, to observe Brownian motion one should have light suspended particles. Brownian motion increases if we increase the temperature. Comparing between different liquids, one with smaller viscosity and smaller density will show more intense Brownian motion.

Einstein developed a theoretical model for Brownian motion in 1905 and deduced the average size of the molecules from it.

BOILING

 The energy of a certain amount of substance is more in its vapour state than in its liquid state. This is because energy has to be supplied to separate the molecules against the attractive forces operating in the liquid phase. If we heat  the liquid, the average kinetic energy of the entire liquid increases and at a certain stage the energy becomes sufficient to break the molecular attraction. The molecules anywhere in the liquid can form vapour bubbles. These bubbles float to the surface of the liquid and finally come out of the liquid. This phenomenon is called boiling and the temperature at which boiling occurs is called boiling point.  Thus, in evaporation, only the molecules near the surface which have kinetic energy greater than the average escape from the liquid, whereas, in boiling, the molecules all over the liquid gain enough energy to become vapour.

The boiling point of a liquid depends on the external pressure over its surface. In fact, boiling occurs at a temperature where the SVP equals the external pressure. Thus, the boiling point of water at 1 atm is 100degree Celsius but at 0.5atm it is 82degree celsius.

Table gives the saturation vapour pressure of water at different temperatures.

 

IDEAL GAS EQUASTION

we have seen that the pressure of all gases changes with temperature in a similar fashion for low pressures. Many of the properties of gases are common at low pressures (and high temperatures, that is, far above their condensation point). The pressure, volume and the temperature in kelvin on such a gas obey the equation

pV=nRT 

where n is the amount of the gas in number of moles and R is a universal constant having value 8.314 J/(K*mol) . The constant R is called the gas constant. Equation is known as ideal gas equation. A gas obeying this equation is called an ideal gas.

LATA MANGESHKAR

Lata mangeshkar, the singer of 'Aei Mere Vatan.....' is nicknamed  'Swar samraagyi' (melody queen ) and 'Swar Kokila'. She was born on 28th september 1929 in a maharastrian family residing in Indore in madhya Pradesh. Her father Deenanath Mangeshkar was himself a noted classical singer and Theatre artist. Her mother's name was Shudhamati. The family's last name used to be Hardikar but Deenanath changed it to Mangeshkar in order to identify his family with his native town, Mangesh in Goa . Lata was named Hridaya at her birth. Her parents later renamed her Lata after a female character Latika in one of her father's plays. The famous singers Asha Bhonsle and Usha Mangeshkar are her younger sisters. Her younger brother Hridatanath is a well -known  music director . Meena is the Youngest sister.