QUANTUM MECHANICS - THE BEGINNING (Part-2)
If you haven’t read the 1st part then, I recommend you to read that first for better understanding. Read here –: Part-1
How the consideration of “Photon” helped to
explain photo-electric effect?
Lets us understand by a simple analogy ; consider red light
photon as a sponge ball and you have to knock out a medium sized heavy plastic
bucket.
Now as each of the red balls has very little mass hence no matter how
much force you apply or, increase the number of red balls they are not going to
knock out the plastic bucket. Now, consider the UV light photon as a heavy
steel ball with a much higher mass that the red one. Thus; if you hit the
bucket with the steel ball with less force or, by a little amount of steel
balls then, you are going to knock out the bucket quite easily.
Same thing happens with light. Each red photon carries a
less amount of energy with it hence, increasing the number of red photons
(intensity) cannot able to trigger the photo-electric effect but, a less
energetic UV light can; as each UV light photon individually carries a much
high amount of energy.
This ground breaking idea of particle nature of light
brought a revolution in the field of physics.
Using the particle nature of light; the ultraviolet
catastrophe also got the explanation and of course; the mystery behind the
light bulb was finally revealed.
This is the time when the modern era of physics actually
begun.
Einstein’s worst nightmare
Einstein unlocked the door to understand the universe in a
whole new perspective by proving the dual nature of light. But, the idea seemed
to challenge the reality and hence generated lots of paradoxes among the
scientist of that era. Light became the battleground for all physicists.
Niels Bohr, a Danish physicist took the command of modern physicist
in the mid 1920's.
In the mid 1920's; an experiment was carried out at Bell
laboratories (New Jersey, America) with electrons.
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| Niels Bohr |
At that time; it was accepted that electrons are small steel
ball like particles revolving around the nucleus inside an atom.
The experiment was about to fire a beam of electrons through
slits upon a crystal and see how it scatters. Well it is similar to firing
paint balls through two gaps upon a screen.
Therefore , the outcome of the experiment was thought to be
quite certain because if you are going to fire two paint balls through two gaps
upon a screen then it definitely going to make two spots upon the screen.
But, the outcomes of the experiment shocked them all.
It has been seen that when electrons fired through the slits
upon the screen; they generate an interference patterns just like other waves.
Waves like light, water etc. creates interference pattern in
which we got some bold (dark) and light fringes alternatively.
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| Electrons showing interference pattern |
In a double slit experiment, a wave is allowed to pass
through two slits and thus the wave travels as two smaller waves .When the top
part (Crest) or, bottom part (trough) of the two waves meet they form a bold
(dark) fringe by adding up together but when crest of one wave meets the trough
of another wave they cancel out each other and form a light fringe as shown in
below figure-:
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| Two light waves interfering with each other to produce a interference pattern |
The behavior of electrons as wave was quite weird because
they are considered as building blocks of everything and now they are showing
shocking results.
Well, how much weird it is?
It’s like you kicked the football towards the goal post with
proper accuracy but as soon as the ball flew in the air it became five or, six
footballs and each of them is as real as the football you kicked.
But, many weird things happen with electrons. For example-:
When the same experiment is carried out by firing a single
electron at a time through a narrow slit upon a screen; then for sometime the
electron appeared as dots on the screen but after that they form a signature
wave pattern.
Just imagine how crazy it is?
In double-slit experiment also; there are two small waves
that interfere with each other but, now only single electron at a time forms a
signature wave pattern.
For analogy; it’s like you fire a bullet on a big wide
screen and instead of making one hole it makes several holes in the screen.
This weird nature of electron and other sub-atomic particles
create a whole new different field of study known as “Quantum mechanics” and
the lead was taken by Niels Bohr.
The probabilistic nature of quantum mechanics became the
worst nightmare of Albert Einstein who is too reluctant to accept the
principles of quantum mechanics.
But, in the other hand; there was Bohr who embraced all odds
and researched on this weird science.
Once in a discussion with Bohr; Einstein said -: “God doesn’t play dice with the universe”
To this statement; Bohr replied -: “You shouldn’t tell God what to do”
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| Bohr & Einstein on a discussion |
This is how the quantum mechanics begun.
“Everything we call
real is made of things we can’t call real”
---- Niels Bohr (1885-1962)
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