This document discusses the history and development of quantum theory through key experiments and scientists. It introduces fundamental concepts like Planck's constant, atomic line spectra, and De Broglie wavelength. Important figures who advanced quantum understanding include Planck, Einstein, Bohr, Heisenberg, Schrodinger, and Feynman. Quantum theory has led to technologies like lasers, semiconductors, and MRI, and may enable future computing and teleportation.

1. Learning ObjectivesLearning Objectives
• Who was involved?Who was involved?
• Which experiments were used to help usWhich experiments were used to help us
understand?understand?
• What are atomic line spectra?What are atomic line spectra?
• Which models were used to represent theWhich models were used to represent the
atom?atom?
• Which equations are fundamental?Which equations are fundamental?
• Which ones are handy to know?!Which ones are handy to know?!
• What have been the successes of quantumWhat have been the successes of quantum
theory?theory?
• What are the future applications?What are the future applications?
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2. Albert Einstein 1879-1955Albert Einstein 1879-1955
• We believe in theWe believe in the
possibility of a theorypossibility of a theory
which is able to give awhich is able to give a
complete description ofcomplete description of
reality, the laws of whichreality, the laws of which
establish relationsestablish relations
between the thingsbetween the things
themselves and notthemselves and not
merely between theirmerely between their
probabilities ... GODprobabilities ... GOD
DOES NOT PLAY DICE.DOES NOT PLAY DICE.

3. Niels Bohr 1885-1962Niels Bohr 1885-1962
• Einstein, DON'T TELLEinstein, DON'T TELL
GOD WHAT TO DO!GOD WHAT TO DO!
• Those who are notThose who are not
shocked when they firstshocked when they first
come across quantumcome across quantum
mechanics cannotmechanics cannot
possibly havepossibly have
understood it.understood it.

4. Werner Heisenberg 1901-1976Werner Heisenberg 1901-1976
• We have to rememberWe have to remember
that what we observe isthat what we observe is
not nature itself butnot nature itself but
nature exposed to ournature exposed to our
method of questioning.method of questioning.
• I, at any rate, amI, at any rate, am
convinced that HE ISconvinced that HE IS
NOT PLAYING ATNOT PLAYING AT
DICE.DICE.

5. Erwin Schroedinger 1887-1961Erwin Schroedinger 1887-1961
• I do not like it, and I amI do not like it, and I am
sorry I ever hadsorry I ever had
anything to do with it.anything to do with it.
• Had I known that weHad I known that we
were not going to get ridwere not going to get rid
of this damned quantumof this damned quantum
jumping, I never wouldjumping, I never would
have involved myself inhave involved myself in
this business!this business!

6. Prince Louis de BrogliePrince Louis de Broglie
1892-19871892-1987
• Electrons should not beElectrons should not be
considered simply asconsidered simply as
particles, but thatparticles, but that
frequency must befrequency must be
assigned to them also.assigned to them also.
(1929, Nobel Prize Speech)(1929, Nobel Prize Speech)

7. Max Planck 1858-1947Max Planck 1858-1947
• Physics is finished, youngPhysics is finished, young
man. It's a dead-endman. It's a dead-end
streetstreet..
(from an unknown teacher(from an unknown teacher
to Planck consideringto Planck considering
Physics at the turn of thePhysics at the turn of the
2020thth
century!)century!)

9. THE ‘ULTRAVIOLET CATASTROPHE’
1900 - Rayleigh
This was a CLASSICAL
prediction, first made in the late
19th century, that an IDEAL
BLACK BODY at thermal
equilibrium will emit radiation
with INFINITE POWER.
Max Planck resolved this issue by
postulating that electromagnetic
energy did not follow the classical
description, but could only
oscillate or be emitted in
DISCRETE PACKETS OF
ENERGY proportional to the
frequency. He called these
packets ‘QUANTA’.
υhE =
Note: sJxh .10626.6 34−
=

10. THE PHOTOELECTRIC EFFECT
1905 - Einstein
The emission of electrons from
a surface (usually metallic)
upon exposure to, and
absorption of, electromagnetic
radiation.
The photoelectric effect was
explained mathematically by
Einstein who extended the
work on QUANTA as
developed by Planck.
φυ −= hKE

11. MILLIKAN’S OIL DROP EXPERIMENT
1909 - Robert Millikan
This experiment
determined the
magnitude of the
electronic charge,
and that it was
QUANTISED.
This value is
approximately
Cx 19
106.1 −
Note: An electron volt (eV) is the amount of energy it takes
to accelerate one electron through a potential of one volt.
Thus, 1eV Jx 19
106.1 −
≡

12. DE BROGLIE WAVELENGTH
Prince Louis de Broglie - 1932
De Broglie
discovered that all
particles with
momentum have
an associated
wavelength.
mv
h
p
h
==λ
What is the wavelength of a human being, assuming he/she
weighs 70 kg, and is running at 25 m/s?

13. NUCLEAR ATOM STRUCTURES
1898 - Thomson

14. 1911 -Rutherford

15. 1913 - Rutherford/Bohr

16. Atomic Line Spectra

17. • General expression:General expression:
• Lyman:Lyman: n>1n>1 (ultraviolet)(ultraviolet)
• Balmer:Balmer: n>2n>2 (visible)(visible)
• Paschen:Paschen: n>3n>3 (infrared)(infrared)
• Brackett:Brackett: n>4n>4 (infrared)(infrared)
• Pfund:Pfund: n>5n>5 (infrared)(infrared)
2
n
hcR
En −=






−= 22
1
1
11
n
R
λ






−= 22
1
2
11
n
R
λ






−= 22
1
3
11
n
R
λ






−= 22
1
4
11
n
R
λ






−= 22
1
5
11
n
R
λ

18. SUMMARY OF IMPORTANT EQUATIONSSUMMARY OF IMPORTANT EQUATIONS
• Energy and frequency:Energy and frequency:
• The photoelectric effect:The photoelectric effect:
• De Broglie wavelength:De Broglie wavelength:
• Angular frequency:Angular frequency:
λ
υ
hc
hE ==
φυ −= hKE
mv
h
p
h
==λ
fπω 2=

19. Equations of interestEquations of interest
(non-examinable!)(non-examinable!)
• Planck’s constant:Planck’s constant:
• Wave vector:Wave vector:
• Schroedinger:Schroedinger:
π2
h
=
λ
π2
=k
Ψ+Ψ∇−=
∂
Ψ∂
V
mt
i 2
2
2



20. Richard Feynman 1918-1988Richard Feynman 1918-1988
• Anyone who has notAnyone who has not
been shocked bybeen shocked by
quantum physics hasquantum physics has
not understood it.not understood it.
• The word 'quantum'The word 'quantum'
refers to this peculiarrefers to this peculiar
aspect of nature thataspect of nature that
goes against commongoes against common
sense.sense.

21. Groucho Marx 1890-1977Groucho Marx 1890-1977
• Very interesting theory - itVery interesting theory - it
makes no sense at allmakes no sense at all!!

22. QUANTUM THEORYQUANTUM THEORY
UsesUses
• LASERsLASERs
• SemiconductorsSemiconductors
• TransistorsTransistors
• LEDLED
• Night Vision GogglesNight Vision Goggles
• CCDCCD
• MRI / PETMRI / PET
ExplainsExplains
• TunnellingTunnelling
• Radioactive decayRadioactive decay
• Periodic tablePeriodic table
(Pauli Exclusion(Pauli Exclusion
PrinciplePrinciple
explanation toexplanation to
Mendeleev’s chart)Mendeleev’s chart)

23. THE FUTURE OF QUANTUM?THE FUTURE OF QUANTUM?
• Dot LASERsDot LASERs
• Logic gatesLogic gates
• ComputingComputing
• Cryptography / EncryptionCryptography / Encryption
• CloningCloning
• TeleportationTeleportation