L11 : Coherent & incoherent source - Wave Optics, Physics, Class 12 Video Lecture

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coherent and incoherent sources these
are some of the facts which you should
know before we start with Young's
double-slit experiment because it was
only after the Young's double-slit
experiment
success that wave nature of light was
fully accepted by everybody right so in
1804 Monsieur performed this experiment
where you will find these terms coherent
and incoherent very often so let us
first understand what are coherent and
incoherent sources when I talk about
coherent sources I am talking about
sources of light which emit waves that
have same frequency and zero or constant
phase difference that means if you have
two sources say s 1 and s 2 we say that
these two sources will be coherent if
they emit waves which have same
frequency as well as they are at zero
phase difference zero phase difference
means they are in the same phase or
constant phase difference that means the
phase difference it is not necessary
that s 1 and s 2 should many many people
tell that coherent source means they
should emit waves that are in same phase
not necessarily same phase they can be
in different phase but the phase
difference should remain the same
throughout the phase difference should
not change so they should rather be at
constant phase difference so here you
can see the example of a laser light so
laser light gives out waves in this
pattern here you can see all these waves
are in the same phase right now
on the other hand when we talk about in
coherent sources they emit waves that
have random frequencies and phase
difference there is no relationship
between the phase different phases and
the frequencies of the different waves
see here you can see that the
they just click random these waves are
like random so examples of incoherent
sources are anything which we see around
us the electric bulb your night lamp or
whatever you see the ordinary light
which you see you around yourself they
are mostly incoherent sources because
they emit waves which have random
frequencies and random fales differences
it's so thick this is coherent and
incoherent sources thank you please
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