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प्रश्न
Precise measurements of physical quantities are a need of science. For example, to ascertain the speed of an aircraft, one must have an accurate method to find its positions at closely separated instants of time. This was the actual motivation behind the discovery of radar in World War II. Think of different examples in modern science where precise measurements of length, time, mass etc. are needed. Also, wherever you can, give a quantitative idea of the precision needed.
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उत्तर १
It is indeed very true that precise measurements of physical quantities are essential for the development of science. For example, ultra-shot laser pulses (time interval ∼ 10–15 s) are used to measure time intervals in several physical and chemical processes.
X-ray spectroscopy is used to determine the inter-atomic separation or inter-planer spacing.
The development of mass spectrometer makes it possible to measure the mass of atoms precisely.
उत्तर २
Extremely precise measurements are needed in modem science. As an example, while launching a satellite using a space launch rocket system we must measure time to a precision of 1 micro second. Again working with lasers we require length measurements to an angstrom unit (1 A° = 10-10m) or even a fraction of it. For estimating nuclear sizes we require a precision of 10-15 m. To measure atomic masses using mass spectrograph we require a precision of 10-30kg and so on.
संबंधित प्रश्न
What do you mean by significant figures?
How many significant figures are present in the 208?
How many significant figures are present in the 500.0?
Round up the following upto three significant figures:
10.4107
How many significant figures should be present in the answer of the following calculation?
0.0125 + 0.7864 + 0.0215
A student measures the thickness of a human hair by looking at it through a microscope of magnification 100. He makes 20 observations and finds that the average width of the hair in the field of view of the microscope is 3.5 mm. What is the estimate on the thickness of hair?
The mean diameter of a thin brass rod is to be measured by vernier callipers. Why is a set of 100 measurements of the diameter expected to yield a more reliable estimate than a set of 5 measurements only?
State the number of significant figures in the following:
2.64 × 1024 kg
State the number of significant figures in the following:
6.032 N m–2
Just as precise measurements are necessary in science, it is equally important to be able to make rough estimates of quantities using rudimentary ideas and common observations. Think of ways by which you can estimate the following (where an estimate is difficult to obtain, try to get an upper bound on the quantity):-
the wind speed during a storm
Solve the numerical example.
Write down the number of significant figures in the following: 0.003 m2, 0.1250 gm cm-2, 6.4 x 106 m, 1.6 x 10-19 C, 9.1 x 10-31 kg.
Write a short note on the following.
Rounding - off
Taking into account of the significant figures, what is the value of 9.99 m – 0.0099 m?
If the density of a solution is 3.12 g mL–1, the mass of 1.5 mL solution in significant figures is ______.
The numbers 2.745 and 2.735 on rounding off to 3 significant figures will give ______.
Using the rules for significant figures, the correct answer for the expression `(0.02858 xx 0.112)/(0.5702)` will be ______.
