The Quantum World
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Index
Index 1
Voorwoord 2
Hoofdstuk 1 2
Science and experiment 2
Light and quantum mechanics 2
Double-slit experiment 4
With bullets 4
With water waves 4
With electrons 5
Hoofdstuk 2 6
Watching electrons 7
Heisenberg’s uncertainty principle 7
Feynman’s quantum paths 8
Hoofdstuk 3 9
De Broglie’s matter waves 9
Hoofdstuk 4 10
Hoofdstuk 5 11
Metals, insulators and semiconductors 13
, Voorwoord
try not to ask the question: ‘but how can it be like that’ since Richard Feynman says ‘nobody
understands quantum mechanics.’
Hoofdstuk 1
Science and experiment
Scientists are perpetually trying to find better explanations in the sense that any new
explanation must not only explain the new puzzle but also be consistent with all of the
previous explanations that still work well.
The hallmark of any theory is that it must be able to make successful predictions and thus it
must be able to say what will happen in any given set of circumstances.
At very small distances involved in the study of atoms and molecules, things do not behave
in a familiar way such as Newton's laws. Quantum mechanics is the explanation for this
behaviour.
Light and quantum mechanics
Newton suggested in the 17th century that light should be regarded as a stream of particles.
In the 19th century, Thomas Young suggested that it was a kind of wave motion. one
property of waves is interference: interference is what happens when two waves collide.
However, at the end of the 19th century, experiments revealed effects that were inexplicable
by the wave theory.
The most famous experiment for this was the photo-electric effect: ultraviolet light shone
onto a negatively charged metal causing it to lose its charge. while shining visible light on the
metal did not do anything.
This was explained by Einstein which was in line with the particle idea of light: the
discharging of the metal was caused by electrons being knocked out of the metal by light
energy concentrated into little bundles of energy also known as photons. According to
Einstein, ultraviolet photons have more energy than visible light photons.
The misunderstanding around this phenomenon was cleared in the 1920s with the
emergence of quantum mechanics. the emergence of quantum mechanics is pioneered by
Heisenberg, Schrödinger and Dirac. this quantum mechanics theory is the theory that
explains the behaviour of all quantum objects.
By using the quantum mechanics theory, the current knowledge about everyday concepts
like waves and particles must be abandoned. the difficulty around quantum mechanics such
------------------------------------------------------------------------------------------------------------------------
Index
Index 1
Voorwoord 2
Hoofdstuk 1 2
Science and experiment 2
Light and quantum mechanics 2
Double-slit experiment 4
With bullets 4
With water waves 4
With electrons 5
Hoofdstuk 2 6
Watching electrons 7
Heisenberg’s uncertainty principle 7
Feynman’s quantum paths 8
Hoofdstuk 3 9
De Broglie’s matter waves 9
Hoofdstuk 4 10
Hoofdstuk 5 11
Metals, insulators and semiconductors 13
, Voorwoord
try not to ask the question: ‘but how can it be like that’ since Richard Feynman says ‘nobody
understands quantum mechanics.’
Hoofdstuk 1
Science and experiment
Scientists are perpetually trying to find better explanations in the sense that any new
explanation must not only explain the new puzzle but also be consistent with all of the
previous explanations that still work well.
The hallmark of any theory is that it must be able to make successful predictions and thus it
must be able to say what will happen in any given set of circumstances.
At very small distances involved in the study of atoms and molecules, things do not behave
in a familiar way such as Newton's laws. Quantum mechanics is the explanation for this
behaviour.
Light and quantum mechanics
Newton suggested in the 17th century that light should be regarded as a stream of particles.
In the 19th century, Thomas Young suggested that it was a kind of wave motion. one
property of waves is interference: interference is what happens when two waves collide.
However, at the end of the 19th century, experiments revealed effects that were inexplicable
by the wave theory.
The most famous experiment for this was the photo-electric effect: ultraviolet light shone
onto a negatively charged metal causing it to lose its charge. while shining visible light on the
metal did not do anything.
This was explained by Einstein which was in line with the particle idea of light: the
discharging of the metal was caused by electrons being knocked out of the metal by light
energy concentrated into little bundles of energy also known as photons. According to
Einstein, ultraviolet photons have more energy than visible light photons.
The misunderstanding around this phenomenon was cleared in the 1920s with the
emergence of quantum mechanics. the emergence of quantum mechanics is pioneered by
Heisenberg, Schrödinger and Dirac. this quantum mechanics theory is the theory that
explains the behaviour of all quantum objects.
By using the quantum mechanics theory, the current knowledge about everyday concepts
like waves and particles must be abandoned. the difficulty around quantum mechanics such
