User:Kishan1986/sandbox

''' Special Theory Of Relativity:

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Introduction: The year 2005 is called the "International year of Physics". Do you know why??..., I will explain you, a century ago ie in 1905 , a clerk by name Albert Einstein presented 3 important topics of modern physics.

1) Light Quanta 2) Brownion motion & Molecular theory 3) Special theory of relativity.

Each of the above papers became the land marks in the history and laid the foundation for major areas of modern physics.

If you consider the light quanta concept it gave birth to "Quantum Physics", "Quantum Theory", " Quantum revolution".

Similarly molecular theory concept laid the foundation for "Molecular Physics", "Molecular Thermodynamics", "Concept of the absolute 0 Kelvin".

Third and last special theory of Relativity gave the relation between "Space-Time","Mass-Energy" and "Electricity-Magnetism".

Lets explain move on to "Special Theory Of Relativity". It can be divided into 8 parts.

1) Whole Einstein Theory is based on 2 postulates.  Postulate 1:			" The laws of physics are same for all observers in all frame of reference"

You may ask what is "Internal frame of reference"????....

I will give you an example.

You are reading this article. i don't know whether you are sitting or standing. If you are at rest or at constant motion that will become your inertial frame of reference. Imagine the chair on which you are sitting is at rest or at constant speed, then that will become your inertial frame of reference. If the same chair is moving at variable velocity which can be considered as accelerating. Now it will not become your frame of reference and you can't apply "Theory of relativity".

You Know??.... In 1915 Eienstin proposed anthor theory called "General Theory of Relativity". You can apply this theory to an acceleratin g chair as well. It is better you make your chair not to accelerate so that i can continue with special theory of relativity.

When you are in an inertial frame, laws of physics like 'optical laws' ,'electromagnetic laws' etc remain same. ex i=r 'angle of incidence should be equal to angle of reflection' holds good in your inertial frame.

Postulate 2: "Speed of light in free space has same value in all direction & in all inertial frame of reference".

Choke to common sense: I will give you 2 examples.

CASE 1: K---> M--> 60 m/s 		40 m/s

K throw ball at M at the speed of 60 m/s and M runs at the speed of 40 m/s away from K. Now M feels Ball is chasing at the speed of 20 m/s (60-40).

CASE2:	K---> <--M 60 m/s 			40 m/s

K throw ball at M at the speed of 60 m/s and M runs at the speed of 40 m/s towards K. Now M feels Ball is chasing at the speed of 100 m/s (60+40).

CASE3: K---> M-->                  c - speed of light c                              c/2

Now K shoots a pulse of light at the velocity c towards M. Now M is running at a speed of c/2. Now tell me what M feels???....Just like above 2 CASES M wont feel c/2.

You know M feels C !!!!!......

This Clearly implies that Newtonian Mechanics applies only for speed much lesser than speed of light not for the speed of light.

2)Time Dilation: "A moving clock ticks more slowly compared to a clock at rest"

3)Twin Paradox: A & B are twins of 20 yrs age, now i am sending A to space at a speed of 0.8c, A returns back after 50 yrs according to B who is on earth. What happens to their age???….

There is a formula t = t0/√(1-(v^2/ c^2)) Now find t/t0

t0= proper time =time interval of clock when it is at rest with respect to observer. t=time interval of clock moving with respect to observer. c=speed of light v=speed of moving body

If you consider velocity of spacecraft as 0.8c, you will get 60%. ie: when A returns from his voyage time will be 30 yrs ( ie 60% of 50 yrs ). If you add initial age 20 yrs for both now B is 70 yrs and age of A is just 50 yrs!!!!!

4)Length Contraction:				"Faster means Shorter"

L= L0√(1- (v^2/c^2))

L<L0 L0=length when object is in rest with respect to observer L=Length when object is in relative motion with respect to observer. C=Speed of light V=Velocity of object or material movement.

It means any object moving will appear to be shorter in the direction of motion. If you put the speed of material in above equation you can find the length contraction.

5)Relativity of Mass:				"Rest mass is least"

m = m0/√(1-(v^2/ c^2)) m0=Mass of object at rest with respect to observer. m=When object is in motion.

The mass of object increases as its speed increases & becomes infinity when speed reaches c. The mass of object is least when it is at rest.

ex: when you catch a ball, it feels more heavier than at rest.

6) Mass Energy Equivalence: 				"Mass and energy are interchangeable"

E=mc^2

E=Energy c=Speed of light m=Mass of object

It says that any body having mass can be converted to equivalent energy. This principle is behind the nuclear power station and nuclear bombs.

7)Doppler Effect:

All of us know about Doppler effect of sound. Lets find the difference between Doppler effect of sound and light. Sound travels through the material medium, and its frame of reference is medium itself. But for light it travels in vacuum or in any material , you can't take inertial frame of reference.

γ=γ0 √ [{(1+(v/c)}/{1-(v/c)}]

γ=Appeared frequency of light γ0= Original frequency of light, when source is at rest wrt to observer. v=Velocity at which the source is moving c=Speed of light

Above equation is applied when source is moving towards observer, when it recedes from observer +ve in eqn becomes -ve.

Hope it has given some knowledge.