Davisson & Germer experiment - Dual Nature of Radiation & Matter Video

hello friends this video on dual nature
of radiation and matter pac-10 is
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more fear from exam please make sure
that you have watched all the videos to
the part nine before going ahead with
path ten so before concluding this
lesson so by this time we have seen that
radiation has dual nature both particle
nature and wave nature and wave nature
we have discussed in our previous
chapter particle nature we discussed
here
similarly matter also has particle
nature which we really don't need to
discuss because we see you backed it all
around us and matter also has a wave
nature which was discussed by D Brock
his hypothesis so that was all about
this lesson which talks about dual
nature of matter and radiation so I hope
now you know what was the purpose of
this lesson right so before concluding
this lesson or before bringing it to an
end let us talk about a very important
experiment performed by a pair a group
of scientists named division and
adjournment what did what so important
or what so significant that they do in
this experiment they actually observed
the diffraction effects of electrons in
crystal diffraction experiment I told
you some time back right that if you
want to observe the wave nature of
electrons you can observe it in crystal
diffraction experiments because the
wavelength associated with an electron
is approximately of the order of the
spacing between atomic crystals so the
Ibiza and German actually perform this
experiment and they could actually
observe the phenomenon of diffraction by
electrons sounds interesting right so
let us see what did they actually do so
first let us look at the experimental
setup which they used so let us look at
the experimental setup diagram looks
little complicated but we will discuss
one by one so it consisted of an
evacuated chamber as you can see this is
the evacuated chamber inside this they
had an electron gun so this is the
electron gun you can see this gun so
from this electrons back ejected there
was a battery
a battery is needed to maintain a
potential difference a cylinder with
fine bone along its axis so this was a
cylinder this a was a cylinder with a
fine hole along its axis there was a
very fine hole small hole along its
tasks so this was the hole a nickel
crystal this is the crystal because the
crystal is needed right we we are
actually doing a crystal diffraction
experiment so what are we trying to do
we will actually try to make the
electrons strike the nickel crystal and
we will see what happens
there was a detector as you can see here
and a galvanometer of course to measure
the amount of current right so these
were these were the different objects
which were required to perform this
experiment now how do what did they
actually do let us see here what they
actually did was this electron beam now
electron beam from this gun was
accelerated by this high voltage power
supply or the battery the one at the
battery which I was talking about was
this high voltage power supply so the
electrons were rejected by this electron
gun and as soon as the electrons came
out here they were accelerated using
this by this battery now these
accelerated electrons we're then made to
pass through the thin hole along the
axis of the cylinder so the cylinder was
placed in such a way that it is placed
it's just in front of the electron gun
so that as soon as the elec beam of
electrons came out of the electron gun
they will get accelerated by the battery
and then they will pass through that
small hole along the axis of the
cylinder now once it comes out through
the other end of the cylinder we get a
very focused beam of electron and a
collimated beam that means too many
electrons along a straight line it it
will not be scattered it is not a
scattered beam a very thin line of
electrons came up and then they were
made to strike this mingle target so
what happened it was seen that the
electrons got scattered by the
terms of nickel so now since electrons
but scattered what happened different
electrons got scattered at different
angles here if you see theta is the
angle of scattering now not all
electrons reached at this point some of
them reached at this point some reach to
this point some reach this plane and so
on so the electrons were scattered by
the atoms of nickel now we had a
detective what was the purpose of the
detector the detector was to detect the
presence of electrons so it was actually
seeing where the electrons are falling
on the screen so it was actually able to
detect the electrons and then the
current associated with this electrons
due to the flow of this electron was
measured using the galvanometer now this
experiment was performed now this
measurement was taken for different
angles of scattering okay and also this
entire experiment was performed for
different voltages that means the
voltage which is supplied by this high
voltage power supply right so it was
performed for different voltages so this
entire experiment was repeated for
voltages 44 volts to 68 volts that means
for what first it was set at forty four
volts so if the electrons are
accelerated by forty four volts then
then also it got scattered at different
angles and it was noted that what was
the angle of scattering and what was the
intensity at what point so the intensity
at all the points were noted and all the
angles of scattering were moving again
it was expa entire thing was repeated
for 45 volts than 46 volts similarly in
st edward's so this experiment was
repeated so many times and then what was
the result to the phenomenon of
diffraction there was a strong p @ v and
at this point of time when there was a
strong teeth the corresponding angle of
scattering was found to be 50 degrees so
when can you get this strong peak
I mean electrons are all particles right
so it has not expected that from
electrons are due to scattering of
electrons you will get some pattern like
this where you have a peak and then mini
mass following it so you
was very similar to the diffraction
pattern right so this diffraction
pattern or the strong peak was due to
the constructive interference right and
then experimentally they also calculated
the wavelength associated with this
electron and this was found that the
wavelength came out to be 0.16 by
nanometers so experimentally the
wavelength associated with this by
looking at the plot or by looking at the
variation of the intensity due to
scattering of electrons they calculated
the wavelength which came out to be
0.165 nanometer right so these were the
two important results of the a basin and
German experiments which clearly showed
that scattering of electrons also gives
rise to diffraction patterns
this shows that electrons also behave
like wave under certain situations this
domestic and German experiment was in
strong agreement with de broglie's
hypothesis how because if they apply D
broccolis hypothesis so according to de
Broglie hypothesis what is the
wavelength associated with an electron
it is H upon P right which in turn comes
out to be one point two to seven divided
by root over capital V where V is the
potential applied to accelerate the
electron we derived this formulae in one
of our previous slides right so now in
this case we told that we observed the P
act v is equal to 54 volts so now in
this formula if you if we put V is equal
to 54 what do we get we get lambda is
equal to one point two two seven divided
by root over 54 which comes out to be
zero point one six seven nanometers so
if you look at it and if you compare it
with the value of wavelength that was
observed experimentally that was zero
point one six five nanometers that means
these two values are in strong agreement
with each other that means division
my experiment was in strong agreement
with de Broglie hypothesis so now that
we have reached towards the end of the
lesson what did we conclude from this
lesson or what did we learn from this
lesson all that we learned here was that
every radiation and every matter has
dual nature they can behave as a
particle they can also behave as a wave
depending upon the experiment when they
are used depending upon the situation
there we are observing them there are
certain phenomenon which can be
explained by wave nature of radiation or
the other hand there are certain
phenomenon like photoelectric effect
which can be explained only by particle
nature of radiation right thank you
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