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Genius Physics
class XI
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2020
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by Manoj
Kumar Sharma
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Physical World
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Science means
organized knowledge.
It is human
nature to observe things and happenings around in the nature and then to relate
them. This knowledge is organized so that it become well connected and logical.
Then it is known as Science. It is a systematic attempt to understand natural
phenomenon and use this knowledge to predict, modify and control phenomena.
Scientific Method
Scientific
methods are used to observe things and natural phenomena. It includes several
steps :
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Observations
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Controlled experiments,
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Qualitative and quantitative reasoning,
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Mathematical modeling,
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Prediction and
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Verification or falsification of theories.
There is no
‘final’ theory in science and no unquestioned authority in science.
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Observations and experiments need theories to support
them. Sometimes the existing theory is unable to explain the new observations,
hence either new theories are formed or modification is done in the existing
theories.
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For example to explain different penomena in light,
theories are changed. To explain bending of light a new Wave-theory was formed,
and then to explain photoelectric effect help of quantum mechanics was taken.
Natural
Sciences can be broadly divided in three branches namely Physics, Chemistry and
biology
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Physics is a study of basic laws of nature and their manifestation in different
phenomenas.
Principal thrusts in Physics
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There are two principal thrusts in Physics;
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1.Unification 2. reduction
Unification
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Efforts are made to explain different phenomena in
nature on the basis of one or minimum laws. This is principle of Unification.
Example:
Phenomena of apple falling to ground, moon revolving around earth and
weightlessness in the rocket, all these phenomena are explained with help of one Law that is, Newtons Law of
Gravitation.
Reductionism
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To understand or to derive the properties of a bigger
or more complex system the properties of its simpler constituents are taken
into account. This approach is
called reductionism.
It is supposed to be the
heart of Physics.
For example
a complex thermo dynamical system can be understood by the properties of its
constituent like kinetic energy of molecules and atoms.
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The scope of Physics can be
divided in to two domains; Macroscopic and Microscopic.
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Macroscopic domain includes phenomena at the level of
Laboratory, terrestrial and astronomical scales.
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Microscopic domain I ncludes atomic, molecular and
nuclear phenomena.
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Recently third domain in between is also thought of
with name Mesoscopic Physics. This deals with group of Hundreds of atoms
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Scope of physics is very wide and exciting because
it deals with objects of size as large as Universe (1025m) and as
small as 10-14 m, the size of a nucleus.
The excitement of Physics is experienced in many fields
Like:
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Live transmissions through television.
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Computers with high speed and memory,
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Use of Robots,
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Lasers and their applications
Physics in relation to other
branches of Science Physics in relation to
Chemistry.
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Chemical bonding, atomic number and complex structure
can be explained by physics phenomena of Electrostatic forces,
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taking help of X-ray diffraction.
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Genius
Physics class XI
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2020
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|
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by Manoj
Kumar Sharma
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Physics in relation to other
Science
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Physics in relation to Biological Sciences: Physics
helps in study of Biology through its inventions. Optical microscope helps to
study bio-samples, electron microscope helps to study
biological cells. X-rays have many applications in biological sciences. Radio
isotopes are used in cancer.
• Physics in relation with
Astronomy:
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Giant astronomical telescope developed in physics are
used for observing planets. Radio telescopes have enabled astronomers to
observe distant limits of universe.
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Physics related to other sciences: Laws of Physics are
used to study different phenomenas in other sciences like Biophysics,
oceanography, seismology etc.
Fundamental Forces in Nature
There is a large number of forces experienced or
applied. These may be macroscopic forces like
gravitation, friction, contact forces and microscopic
forces like electromagnetic and inter-atomic forces.
But all these forces arise from some basic forces called
Fundamental Forces.
Fundamental Forces in Nature..
1. Gravitational force.
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It is due to Mass of the two
bodies.
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It is always attractive.
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It operates in all objects
of universe.
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Its range is infinite
It’s a weak force. 10-38 times
compared to strong Nuclear force
2.Electromagnetic Forces:
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It’s due to stationery or moving Electrical charge
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It may be attractive or repulsive.
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It operates on charged particles
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Its range is infinite
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Its stronger 1036 times than
gravitational force but 10-2 times of strong Nuclear force.
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Its range is very short, within nuclear size (10-15 m).
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Its strongest force in nature
4.Weak Nuclear force:
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Operate within nucleons I.e. elementary particles like
electron and neutrino.
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It appears during radioactive b decay.
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Has very short range 10-15m.
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10-13 times than Strong nuclear force.
Conservation Laws
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In any physical phenomenon governed by different
forces, several quantities do not change with time. These special quantities
are conserved
quantities of nature.
1.For motion
under conservative force, the total mechanical Energy of a body is constant.
2.Total
energy of a system is conserved, and it is valid across all domains of nature
from microscopic to macroscopic. Total energy of the universe is believed to be
constant.
3.Conservation
of Mass was considered another conservation law, till advent of Einstein. Then
it was converted to law of conservation of mass plus energy. Because mass is
converted into energy and vice-versa according to equation E = mc2 The
examples are annihilation and pair production.
4.Momentum is another
quantity which is preserved.
Similar is
angular momentum of an isolated system. 5.Conservation of Electric charge is a
fundamental law of nature.
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Later there was development of law of conservation of
attributes called baryon number, lepton number and so on.
The laws of
nature do not change with change of space and time. This is known as symmetry
of space and time. This and some other symmetries play a central role in modern
physics. Conservation laws are connected to this.
3. Strong nuclear force:
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Operate between Nucleons
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It may be attractive or repulsive
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