introduction,special theory of relativity,time dilation ,length contraction

1. CIAL THEORY OF RELATIVITY
TIME DILATION &
LENGTH CONTRACTION
Submitted by :-
AKASH SINGH CHAUHAN
B.TECH 1ST YEAR
( 2ND SEMESTER)
Submitted to :-
Ms. NISHA CHUGH
ASST. PROFESSOR

2. CONTENTS
• INTRODUCTION
• SPECIAL THEORY OF RELATIVITY
• POSTULATES
• TIME DILATION
• LENGTH CONTRACTION
• TWIN PARADOX
• BIBLIOGRAPHY

3. BORN - 14TH MARCH 1879
DIED - 18TH APRIL 1955

4. SPECIAL THEORY OF RELATIVITY
• A German scientist ALBERT EINSTEIN
concluded that the concepts of space
& time are to be revised . In 1905 , at
the age of 26 . He proposed a theory
which is known as SPECIAL THEORY
OF RELATIVITY.

5. POSTULATES
• The special theory of relativity based on following
two postulates :
1. THE PRINCIPLE OF RELATIVITY : All the laws of
physics are the same in all inertial frame of
reference.
2. THE PRINCIPLE OF INDEPENDENCE OF THE
VELOCITY OF LIGHT : The speed of light in a
vacuum is independent of the motion of the
light source or receiver.

6. TIME DILATION
• “ Time dilation is the phenomenon of slowing
down of a clock , as determined by an observer
who is in relative motion with the clock”
• As it is an relative thus the extent of dilation
depends upon the relative velocity of the clock
w.r.t the observer.
• It is an very important consequence of the
“SPECIAL THEORY OF RELATIVITY”.

11. The total time for the light pulse to trace its path is given by
The length of the half path can be calculated as a function
of known quantities as
Substituting D from this equation into the previous and solving
for Δt' gives:
and thus, with the definition of Δt:

12. THE TWIN PARADOX
• The time dilation effect leads to the famous
“THE TWIN PARADOX” of special relativity .let
us consider a hypothetical experiment
involving twin sisters SEETA and GEETA .After
celebrating 20th birthday .the adventurous
twin sets out a space voyage ….................

13. THE TWIN PARADOX

14. LENGTH CONTRACTION
“Length contraction is the phenomenon of decrease in length
measured by the observer , of an object which is traveling at
any non-zero velocity relative to the observer”.
• This contraction formally called Lorentz contraction or Lorentz - fitzgerald
contraction after Hendrik Lorentz and George fitzgerald.
• This contraction is usually only noticeable at a substantial fraction of the speed of
light.
• Length contraction is only in the direction parallel to the direction in which the
observed body is travelling.
• This effect is negligible at everyday speeds , and can be ignored for all regular
purposes . only at greater speeds does it become relevant. At a speed of
13,400,000m/s(30 million mph,0.0447c),the contracted length is 99.9% of the
length at rest: at a speed

20. LENGTH CONTRACTION DERIVATION
• Where
• L0 is the proper length (the length of the object in its rest frame),
• L is the length observed by an observer in relative motion with respect to
the object,
• v is the relative velocity between the observer and the moving object,
• c is the speed of light,
and the Lorentz factor, γ(v), is defined as
•

21. BIBLIOGRAPHY
• TIME DILATION
• L.LANDAU , YU.RUMER -1981-MIR PUBLICATION
MOSCOW.
• LENGTH CONTRACTION
• R.RESNICK , D. HALLIDAY , FIFTH EDITION , JOHN
WILLEY & SONS INC. SINGAPORE