Transcript Wave – Particle Duality of Energy and Matter

By: Conor Donohue and Jen Davis
Waves are everywhere. But what makes a
wave a wave?
What characteristics, properties, or
behaviors are shared by all the phenomenon
which we typically characterize as being a
wave? How can waves be described in a
manner that allows us to understand their
basic nature and qualities?
A
wave can be described as
a disturbance that travels
through a medium from
one location to another
location.
 The
repeating and periodic
disturbance which moves through
a medium from one location to
another is referred to as a wave.
A
slinky would be an example of a
wave.
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Introduced the theory of
electron waves, including
wave –particle duality and
the theory of matter.
According to de Broglie, a
particle is a wave.
He proposed that the
relationship of wavelength
lambda to momentum p
would determine the
wavelength of any matter, in
the relationship: l
lambda = h / p .
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Performed a classic
experiment in which a
beam of electrons of
known momentum (p) was
directed at an angle onto a
nickel surface. The angles
of reflected electrons were
measured and the results
matched up with de
Broglie's hypothesis for
electron wavelength.
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A wave-particle dual has been found to be
characterized by electrons
The Davisson and Germer model established the
evidence of wave nature with electrons
The evidence for the description of light as waves
is proven by the photoelectric effect which shows
evidence of particle nature.
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The photoelectric effect refers to the emission, or
ejection, of electrons from the surface of,
generally, a metal in response to incident light.
Energy contained within the incident light is
absorbed by electrons within the metal, giving
the electrons sufficient energy to be 'knocked'
out of, that is, emitted from, the surface of the
metal.
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Particle duality exhibits both wave-like and
particle-like properties
The central concept of "particle" and "wave" fully
describes the behavior of quantum mechanics
Quantum mechanics are a set of scientific
principles describing the known behavior of
energy and matter.
The uncertainty principle states that certain pairs
of physical properties, like position and
momentum.
- Δ here indicates standard deviation, a measure of
spread or uncertainty;
- x and p are a particle's position and linear
momentum respectively.
- is the reduced Planck's constant (Planck's
constant divided by 2π).
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The baseball displays
wave-particle duality: the
path of the baseball could
not be precisely
determined. The map
shows where a "pitched"
electron will cross home
plate.
The probability of finding
the electrons at various
locations outside the
nucleus and on the field is
shown on the map.
The probability map is
called an orbital.
1) A wave can be described as
a) disturbance that travels through a medium
from one location to another
b) distance from one location to another
c) an ocean current
d) a hand gesture used to say hello/goodbye
2) True/false
A slinky could be used as an example of a
wave.
3) According to de Broglie, a __________is a wave.
a)
Particle
b)
Nucleus
c)
Scientist
4) A wave-particle dual has been found to be
characterized by
a)
Protons
b)
Neutrons
c)
Electrons
d)
The Nucleus
5) True/False
Quantum mechanics are a set of scientific principles
describing the known behavior of energy and matter.
6) The photoelectric effect refers to the emission,
or ejection, of
from the surface of,
generally, a metal in response to incident light.
a)
Protons
b) Electrons
c)
Neutrons
d) Photo-electricons
7) What is the formula of uncertainty principle?
a)
b)
c)
d)
E=mc^2
F=ma
A=b*h
8) Which picture shows particle duality
a)
c)
b)
d)
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1)
2)
3)
4)
5)
6)
7)
8)
A
True
A
C
True
B
A
C
Energy + Matter
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Publicized early in the debate about
whether light was composed of particles or
waves, a wave-particle dual nature soon
was found to be characteristic of electrons
as well.
The evidence for the description of light as
waves was well established at the turn of
the century when the photoelectric effect
introduced firm evidence of a particle
nature as well.
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The particle properties of electrons was well
documented when the DeBroglie hypothesis
and the subsequent experiments by Davisson
and Germer established the wave nature of
the electron.
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The details of the photoelectric effect were
in direct contradiction to the expectations
of very well developed classical physics.
The explanation marked one of the major
steps toward quantum theory.
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The remarkable aspects of the photoelectric
effect when it was first observed were:
1. The electrons were emitted immediately - no time lag!
2. Increasing the intensity of the light increased
the number of photoelectrons, but not their maximum kinetic
energy!
3. Red light will not cause the ejection of electrons, no
matter what the intensity!
4. A weak violet light will eject only a few electrons, but
their maximum kinetic energies are greater than those for
intense light of longer wavelengths!
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Analysis of data from the photoelectric
experiment showed that the energy of the
ejected electrons was proportional to the
frequency of the illuminating light.
Whatever was knocking the electrons out had
an energy proportional to light frequency.
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http://phet.colorado.edu/simulations/sims.p
hp?sim=Photoelectric_Effect
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Although it is difficult to draw a line separating wave–particle
duality from the rest of quantum mechanics, it is nevertheless
possible to list some applications of this basic idea.
Wave–particle duality is exploited in electron microscopy,
where the small wavelengths associated with the electron can
be used to view objects much smaller than what is visible
using visible light.
Similarly, neutron diffraction uses neutrons with a wavelength
of about one ångström, the typical spacing of atoms in a
solid, to determine the structure of solids.
1.
2.
3.
4.
5.
Bill and Ted’s experiments established the wave nature of
the electron. T/F
The details of the photoelectric effect were NOT in direct
contradiction to the expectations of very well developed
classical physics. T/F
Wave-particle duality is exploited in electron microscopy.
T/F
The explanation of the photoelectric effect marked one of
the major steps toward quantum theory. T/F
Analysis of data from the photoelectric experiment showed
that the energy of the ejected electrons was proportional to
the frequency of the illuminating light. T/F