Difference between revisions of "Physics"
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* Thermodynamics | * Thermodynamics | ||
* Electromagnetism | * Electromagnetism | ||
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| − | + | == Modern Physics == | |
| − | Modern Physics | ||
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== Mechanics == | == Mechanics == | ||
| − | + | {{main|mechanics}} | |
| − | Etymologically, the study of machines is called Mechanics. It broadly covers kinematics, mechanical | + | Etymologically, the study of machines is called Mechanics. It broadly covers [[kinematics]], mechanical [[force]]s, [[work]], [[power]], and [[energy]], and various properties of [[matter]]. |
Kinematics is the study of (relative) motion - displacement, velocity, acceleration etc. The two relations at the heart of kinematics are: | Kinematics is the study of (relative) motion - displacement, velocity, acceleration etc. The two relations at the heart of kinematics are: | ||
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The simplest topic under kinematics is uniform rectilinear motion. Other simple topics are projectile motion, uniform circular motion, simple harmonic motion etc. | The simplest topic under kinematics is uniform rectilinear motion. Other simple topics are projectile motion, uniform circular motion, simple harmonic motion etc. | ||
| − | + | The rules of physics are almost fully summarized by the three famous laws of motion due to [[Isaac Newton]]: | |
* A body continues to be in its state of uniform rectilinear motion until it is disturbed by an external force. This property is known as inertia. | * A body continues to be in its state of uniform rectilinear motion until it is disturbed by an external force. This property is known as inertia. | ||
* The rate of change of momentum of a body with respect to time is directly proportional to the force acting on it. | * The rate of change of momentum of a body with respect to time is directly proportional to the force acting on it. | ||
* Every action as an equal and opposite reaction. | * Every action as an equal and opposite reaction. | ||
| − | + | [[Mass]] is the one of the two most basic intrinsic properties of a body. It is a measure of its [[inertia]]. [[Momentum]] is defined as the [[product]] of the mass and [[velocity]] of a body. [[Force]] is something that changes or tends to change the momentum of a body, or, informally, "a push or pull". | |
| − | Mechanical work is defined by the relation <math>W =\int^{x_f}_{x_i} F\,dx</math> where <math>W</math> is work done, <math>F</math> is force, <math>x</math> is displacement, and subscripts <math>i</math> and <math>f</math> denote the initial and final states respectively. Similarly, mechanical power is defined as <math>P =\int^{v_f}_{v_i} F\,dv</math> where <math>P</math> is power delivered and <math>v</math> is velocity. Energy is the other basic intrinsic property of a body. Mechanical energy is simply the capacity of a body to do mechanical work. | + | Mechanical [[work]] is defined by the relation <math>W =\int^{x_f}_{x_i} F\,dx</math> where <math>W</math> is work done, <math>F</math> is force, <math>x</math> is displacement, and subscripts <math>i</math> and <math>f</math> denote the initial and final states respectively. Similarly, mechanical [[power]] is defined as <math>P =\int^{v_f}_{v_i} F\,dv</math> where <math>P</math> is power delivered and <math>v</math> is velocity. [[Energy]] is the other basic intrinsic property of a body. Mechanical energy is simply the capacity of a body to do mechanical work. |
| − | Among the various properties of matter are elasticity, surface tension, viscosity etc. | + | Among the various properties of matter are elasticity, surface tension, viscosity etc. The most important one is [gravity]]. Gravity is indeed considered one of the most mysterious things not only in physics but in [[science]] as a whole. |
| − | == | + | == Acoustics == |
| − | + | {{main|Acoustics}} | |
| − | + | Acoustics is etymologically the study of ]]sound\\. Sound waves are mechanical waves - they travel by actual vibrations in some material medium. Acoustics concerns itself with mechanical [[wave]]s in general. Phenomena such as forced [[vibration]]s, [[resonance]], damped vibrations and [[Doppler effect]] come under this branch of physics. | |
== Optics == | == Optics == | ||
| − | + | {{main|Optics}} | |
| − | Etymologically, optics is the study of vision. Light waves are electromagnetic waves - they consist of mutually perpendicular electric fields and magnetic | + | Etymologically, optics is the study of vision. [[Light]] waves are electromagnetic waves - they consist of mutually perpendicular electric fields and [[magnetic field]]s, and can travel through vacuum. Optics is the study of electromagnetic waves in general. So it covers all waves in the [[electromagnetic spectrum]] given below: |
| − | * Gamma rays | + | * [[Gamma rays]] |
| − | * X - Rays | + | * [[X-Rays]] |
| − | * Ultraviolet | + | * [[Ultraviolet rays]] |
| − | * Visible light | + | * [[Visible light]] |
| − | * Infrared Rays | + | * [[Infrared Rays]] |
| − | * Microwaves | + | * [[Microwaves]] |
| − | * | + | * [[Radio waves]] |
| − | + | One of the most controversial questions in optics is whether light is an wave or a ray. Accordingly there are two branches of optics, but only ray optics belongs to classical physics. Wave optics are a topic of modern physics. In ray optics covers topics such as reflection and refraction, and the dispersion of white light into its constituent colors. | |
== Thermodynamics == | == Thermodynamics == | ||
| − | + | {{main|Thermodynamics}} | |
| − | + | Thermodynamics does not have a direct etymological meaning, but it could be named the study of [[heat]] transfer. Anything in physics related to heat comes under thermodynamics. | |
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== Electromagnetism == | == Electromagnetism == | ||
| − | + | {{main|Electromagnetism}} | |
| − | + | Electromagnetism is the combined study of [[electricity]] and [[magnetism]], and the most important addition to classical physics after [[Newton]]'s work. | |
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== See also == | == See also == | ||
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* [[Physics scholarships]] | * [[Physics scholarships]] | ||
* [[Physics summer programs]] | * [[Physics summer programs]] | ||
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| + | [[Category:Physics]] | ||
Revision as of 19:10, 10 December 2007
The study of energy is known as physics. That is the most general definition of physics you can think of, which gives one some idea of the vastness of topics coming under physics. Everything concerning energy in some form or the other is covered by physics.
Contents
Branches of Classical Physics
Physics as we knew it till the end of the nineteenth century is known now as Classical physics. It is broadly classified into the following branches:
- Mechanics
- Accoustics
- Optics
- Thermodynamics
- Electromagnetism
Modern Physics
The twentieth century ushered in the two new broad topics of a) relativity and b) quantum physics. Unification of these two theories and the sub topic of particle physics are the subjects of twenty-first century physics.
Mechanics
- Main article: mechanics
Etymologically, the study of machines is called Mechanics. It broadly covers kinematics, mechanical forces, work, power, and energy, and various properties of matter.
Kinematics is the study of (relative) motion - displacement, velocity, acceleration etc. The two relations at the heart of kinematics are:
, and
where 
is displacement, 
is velocity, 
is acceleration, and 
is time.
The simplest topic under kinematics is uniform rectilinear motion. Other simple topics are projectile motion, uniform circular motion, simple harmonic motion etc.
The rules of physics are almost fully summarized by the three famous laws of motion due to Isaac Newton:
- A body continues to be in its state of uniform rectilinear motion until it is disturbed by an external force. This property is known as inertia.
- The rate of change of momentum of a body with respect to time is directly proportional to the force acting on it.
- Every action as an equal and opposite reaction.
Mass is the one of the two most basic intrinsic properties of a body. It is a measure of its inertia. Momentum is defined as the product of the mass and velocity of a body. Force is something that changes or tends to change the momentum of a body, or, informally, "a push or pull".
Mechanical work is defined by the relation 
where 
is work done, 
is force, is displacement, and subscripts 
and 
denote the initial and final states respectively. Similarly, mechanical power is defined as 
where 
is power delivered and is velocity. Energy is the other basic intrinsic property of a body. Mechanical energy is simply the capacity of a body to do mechanical work.
Among the various properties of matter are elasticity, surface tension, viscosity etc. The most important one is [gravity]]. Gravity is indeed considered one of the most mysterious things not only in physics but in science as a whole.
Acoustics
- Main article: Acoustics
Acoustics is etymologically the study of ]]sound\\. Sound waves are mechanical waves - they travel by actual vibrations in some material medium. Acoustics concerns itself with mechanical waves in general. Phenomena such as forced vibrations, resonance, damped vibrations and Doppler effect come under this branch of physics.
Optics
- Main article: Optics
Etymologically, optics is the study of vision. Light waves are electromagnetic waves - they consist of mutually perpendicular electric fields and magnetic fields, and can travel through vacuum. Optics is the study of electromagnetic waves in general. So it covers all waves in the electromagnetic spectrum given below:
One of the most controversial questions in optics is whether light is an wave or a ray. Accordingly there are two branches of optics, but only ray optics belongs to classical physics. Wave optics are a topic of modern physics. In ray optics covers topics such as reflection and refraction, and the dispersion of white light into its constituent colors.
Thermodynamics
- Main article: Thermodynamics
Thermodynamics does not have a direct etymological meaning, but it could be named the study of heat transfer. Anything in physics related to heat comes under thermodynamics.
Electromagnetism
- Main article: Electromagnetism
Electromagnetism is the combined study of electricity and magnetism, and the most important addition to classical physics after Newton's work.
