Special Relativity (4.1) Complete Questions and
Answers with Verified Solutions 100% Correct |
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Special relativity
• describe an example of natural phenomena that cannot be explained by
Newtonian physics, such as the presence of muons in the atmosphere -
ANSWER Problems that had resisted explanation using the Newtonian
approach:
- light appeared to be a wave, but the medium for its propagation (the 'aether')
was undetectable
- the equations describing electricity and magnetism were inconsistent with
Newton's descriptions of space and time
Additionally, the problem of accounting for the lifetime of muons at different
altitudes could not be explained by Newtonian physics. Scientists measured the
amount of muons present in the atmosphere at the top of a mountain, compared
to the bottom.
From 563/hr at the top, Newtonian calculations predicted 27/hr at sea level.
407/hr were counted; aligning with the theory of special relativity.
It was found that to the observers, the distance was 1910 m. To the muons, it was
183 m. This is called 'length contraction'.
The mean lifetime in the muon's frame of reference is 2.2us, but in the observers
it was 23us, so to the scientists they took longer to decay: known as 'time
dilation'.
, Special relativity
• define the terms frame of reference and inertial frame of reference -
ANSWER When you describe the motion of an object, you need something to
compare it against. The frame of reference is an arbitrary set of axes with
reference to which the position or motion of something is described, or physical
laws are formulated. It defines the location of the observer.
In general, a frame of reference that is stationary or moving at constant velocity is
an inertial frame. However, in a frame of reference that is accelerating, results are
different.
The surface of Earth is considered inertial even though undergoing centripetal
acceleration (small enough to be disregarded).
Special relativity
• recall the two postulates of special relativity - ANSWER Two assumptions or
'postulates' of special relativity:
1. the laws of physics are the same in all inertial (uniformly moving) frames of
reference
2. the speed of light in a vacuum has the same value, c, in all inertial frames of
reference
The second postulate can be said to be redundant, as it is a logical consequence of
the first
Special relativity
• recall that motion can only be measured relative to an observer - ANSWER
(On a train) You are moving relative to the stationary observer outside the train,
but the stationary observer is moving relative to you. There is no way of working
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