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# CBSE Notes for Class 11 Physics chapter Physical world in english Medium

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## Physical world

#### Introduction of physics

- What is science?

Science : Organised knowledge of nature is known as science.

"Science is a systematic attempt to understand natural phenomena in as much detail and depth as possible, and use the knowledge so gained to predict, modify and control phenomena. Science is exploring, experimenting and predicting from what we see around us."

Physics is study of nature and its phenomenoms.

Thrust area of study of physics:

(i) Unification: Measuring unit in special manner and unified.

Unification is to explain different phenominom in nature on basis of one or minimum law.

(ii) Reductionism: A related effort is to derive the properties of a bigger, more complex, system from the properties and interactions of its constituent simpler parts. This approach is called reductionism and is at the heart of physics.

Science is not based on assumptions while it is based on experiments.

• All theories/principles in science is not final it can be changed on scienctific study.
•

Scientific Method to study nature / Scienctific study.

(i) Obsorvation:

(ii) Controll experiment

(iii) Qualitative & quantitive reasoning: Quantitative measurement is central to the growth of science, especially physics, because the laws of nature happen to be expressible in precise mathematical equations. The second most important insight was that the basic laws of physics are universal — the same laws apply
in widely different contexts. Lastly, the strategy of approximation turned out to be very successful.

(iv) Mathematical Modelling (Making Formula/testing on formula) :

(v) Prediction : Pridiction will be true or false

(i)

(v) Verification or

There are two domains of interest:

(i) Macroscopic: The macroscopic domain includes phenomena at the laboratory, terrestrial and astronomical scales.
(ii) Microscopic: The microscopic domain includes atomic, molecular and nuclear phenomena.

Classical Physics deals mainly with macroscopic phenomena and includes subjects like Mechanics, Electrodynamics, Optics and Thermodynamics.

Electrodynamics deals with electric and magnetic phenomena
associated with charged and magnetic bodies.

Important facts for science.

• Modified Hypothethis or principle
• Microscopic observations of events.
• Making hypothesis or principle on the basis of observations.
• Testing and analysing these hypothesis or principles which really happens.

Discussion facts:

• Prediction on the study and its proving.

It covers a tremendous range of magnitude of physical quantities like length, mass, time, energy, etc. At one end, it studies phenomena at the very small scale of length (10-14 m or even less) involving electrons, protons, etc.; at the other end, it deals with astronomical
phenomena at the scale of galaxies or even the entire universe whose extent is of the order of 1026 m.

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