الخواص الجسيمية للموجات / الفصل الثاني

end of 19th century:
• almost all of physics seemed to be explained by
mechanics, thermodynamics & electromagnetism
• only a few “minor” problems remained to be resolved.
otherwise physics was thought to be almost complete, it
was just a question of time…
• nature of problems: there were quite solid “buildings”
of mechanics, electricity and magnetism without
communications between them.
• there were also mysterious effects that lacked
explanation, but they did not affect machinery, weaponry,
or agriculture. only a few people were bothered by these
unsolved problems.
the dilemma of mechanics and e&m
the problem can be stated in the following form there
are three statements
? galilean transformations of coordinates and absolute
time.
? the speed of light is constant in all frames of
reference.
? all laws of nature are the same in all inertial frames of
reference.
? these three statements contradict each other. one has
to be dropingped to resolve the problem.
the special theory of relativity
? einstein’s solution – special theory of relativity: two
postulates, 1905:
? all inertial frames of reference are equally suitable
for the description of physical phenomena.
? the speed of light in vacuum is the same for all
observers and is independent of the motion of the
source.
? the toll for this is the lorentz transformations of
space-time with a set of consequences – the effects
not intuitively simple for most people
nature and nature’s laws lay hid in night,
god said, “let newton be,” and all was light.
it did not last the devil howling “ho! let
let einstein be!” restored the status quo.
alexander pope – sir john collins
three big problems with light (em
radiation) that were unresolved:
• blackbody radiation
• photoelectric effect
• atomic spectra
today we will start discussion of how
“fixing” these three problems has changed
the world.
blackbody raditation
bodies emit heat radiation that depends on their
temperature.
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0.0029
wien
slaw
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