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                                UNIT 2              STRUCTURE OF ATOM The existence of atoms has been proposed since the times of early Indian and Greek philosophers around 400B.C.Anlndian philosopher Maharishi Kanad postulated that it we go on dividing matter (padarth), we shall ultimately get smallest particle beyond which further division will not be possible. He ancient Greek named these particles as parmanu. Around the same era, ancient Greek philosophers Democritus and Leucippus suggested that if we go on dividing matter, a stage will come when particles obtained cannot be divided further. Democritus called these particles as atoms. The word 'atom' has been derived i from the Greek word 'a-tomio' meaning un cutable or non-divisible. However all these ideas were based on philosophical considerations and not much experimental work to validate these ideas could be done t...

 Physics                  UNIT - I                            CHAPTER - 5                                   Error Analysis      SIGNIFICANT FIGURES  The significant figures express the accuracy with which a physical quantity may be expressed  The digits whose values are accurately known in a particular measurement, are called is significant figures  Greater. the number significant figures obtained when making a measurement, more Conversely, a measurement made to only a few significant accurate is the measurement. figures is not. a very occur a one. For example, a recorded figure of 1-21 means the relied on as accurate to three significant figures and a figure of 1-212 is quantity can bei qua he accurate to four significant figures. Thus, significant figur...

PHYSICS                                                  4                     Dimensional Analysis DIMENSIONS OF A PHYSICAL QUANTITY The derived units of all the physical quantities can be suitably expressed in terms The derived units o Tne mental units of mass, length and time raised to some power)For example, of the if   units of mass, length and time are denoted by bracketed capital letters [M], [L] and (TI, then for area (=length x breadth), we have       area = [L] × [L] = [L]² Further, as in expressing area, units of mass and time do not occur, we write    area = [M° L² T°] The dimensions of area are zero in mass, two in length and zero in time. Similarly, for velocity, we have    Velocity = Distance / time = [L]/[T] = [L T¹]         ...

Physics                                                   3        Length Mass And Time Measurements ORDER OF MAGNITUDE OF LENGTH Sometimes, it is sufficient to know the order of the magnitude of a quantity instead of knowing its absolute value. For this, if a number is less than 5, it is taken as 1 and if it lies between 5 and 10, it is taken as 10. For example, the velocity of light is 3 x108 ms.However, the order of magnitude of the velocity of light is regarded as 108 ms Here, 3 has been regarded as 1, as it is less than 5). Again, number of seconds in one minute is 60 or 6 x 10. The order of magnitude of seconds in a minute is taken as 102 (Here, 6 has been regarded as 10, as it is greater than 5).  In this universe, the various objects have lengths over a wide range. The following table gives order of magnitude of their lengths (from...

  Physics                                     2                        System of Units NEED FOR MEASUREMENT  In physics, much importance is attached to measurements and for this reason. it is sometimes called as an exact science or the science of measurement. Lord Kelvin once remarked that:  When you can measure what you are speaking about and express it in numbers, you know WE something about it ; but when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind." In making this statement, Lord Kelvin had actually highlighted the importance of having the quantitative knowledge (measurement) of a physical quantity. We know that in order to move a body, force has to be applied. The force so applied will produce some acceleration in the motion of the body. But how much acceleration will be produc...