Quantum mechanics describes the motion of particles at the atomic scale. Albert Einstein's explanation of the photoelectric effect showed that light behaves as particles called photons. The photoelectric effect demonstrates that electrons can be emitted from metals when light of a high enough frequency strikes the surface. Kinetic energy of emitted electrons is determined by the frequency of light and the work function of the metal. This supported the idea that light has both wave-like and particle-like properties, leading to the development of electron microscopes that use electrons' wave-like behavior.
The Compton effect is the result of a high-energy photon colliding with a target, which releases loosely bound electrons from the outer shell of the atom or molecule .
The Compton effect is the result of a high-energy photon colliding with a target, which releases loosely bound electrons from the outer shell of the atom or molecule .
60508_paticle like properties of waves.pptxClaireSadicon
Discussion of Properties of Waves
The particle-like properties of electromagnetic radiation
Classical Postulates
Einstein theory
Black Body Radiation
Stefan's radiation law
Wein's displacement law
Rayleigh-Jeans Formula
Planck’s Theory and Radiation Law
The Compton Effect
Bremsstrahlung and X-Ray Production
Pair production
Electron-Positron Annihilation
it describes the bony anatomy including the femoral head , acetabulum, labrum . also discusses the capsule , ligaments . muscle that act on the hip joint and the range of motion are outlined. factors affecting hip joint stability and weight transmission through the joint are summarized.
Introduction to AI for Nonprofits with Tapp NetworkTechSoup
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A review of the growth of the Israel Genealogy Research Association Database Collection for the last 12 months. Our collection is now passed the 3 million mark and still growing. See which archives have contributed the most. See the different types of records we have, and which years have had records added. You can also see what we have for the future.
Exploiting Artificial Intelligence for Empowering Researchers and Faculty, In...Dr. Vinod Kumar Kanvaria
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International FDP on Fundamentals of Research in Social Sciences
at Integral University, Lucknow, 06.06.2024
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2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
This webinar will introduce you to my framework, highlighting the key competencies I identified from my research. It will also show how anybody involved in language teaching (any language, not just English!), teacher training, managing schools or developing language learning materials can benefit from using the framework.
2. Quantum?
Quantum mechanics is the study of processes
which occur at the atomic scale.
The word "quantum" is derived
From Latin to mean BUNDLE.
Therefore, we are studying the motion of
objects that come in small bundles called
quanta. These tiny bundles that we are
referring to are electrons traveling around
the nucleus.
3. “Newton, forgive me..”, Albert Einstein
At the atomic scale Newtonian Mechanics
cannot seem to describe the motion of
particles. An electron trajectory between
two points for example IS NOT a perfect
parabolic trajectory as Newton's Laws
predicts. Where Newton's Laws end
Quantum Mechanics takes over.....IN A
BIG WAY!
One of the most popular concepts
concerning Quantum Mechanics is
called , “The Photoelectric Effect”. In
1905, Albert Einstein published this
theory for which he won the Nobel Prize
in 1921.
4. What is the Photoelectric Effect?
In very basic terms, it is when electrons are
released from a certain type of metal upon
receiving enough energy from incident light.
So basically, light comes down and strikes the
metal. If the energy of the light wave is
sufficient, the electron will then shoot out of the
metal with some velocity and kinetic energy.
5. The Electron-Volt = ENERGY
Before we begin to discuss the photoelectric
effect, we must introduce a new type of unit.
Recall:
This is a very useful unit as it shortens our calculations and allows us to
stray away from using exponents.
6. The Photoelectric Effect
"When light strikes a material, electrons are
emitted. The radiant energy supplies the work
necessary to free the electrons from the
surface."
7. Photoelectric Fact #1
The LIGHT ENERGY (E) is in the form of quanta
called PHOTONS. Since light is an
electromagnetic wave it has an oscillating
electric field. The more intense the light the
more the field oscillates. In other words, its
frequency is greater.
9. More on Fact #1
λλ
α
hc
Ef
c
h
f
E
hfEfE
=→=
=→=→
h hc
6.63x10-34
Js 1.99x10-25
Jm
4.14x10-15
eVs 1.24x103
eVnm
Make sure you USE the correct constant!
Planck’s Constant is the SLOPE of an
Energy vs. Frequency graph!
10. Photoelectric Fact #2
The frequency of radiation must be above a certain value
before the energy is enough. This minimum frequency
required by the source of electromagnetic radiation to just
liberate electrons from the metal is known as threshold
frequency, f0.
The threshold frequency
is the X-intercept of the
Energy vs. Frequency
graph!
11. Photoelectric Fact #3
Work function, φ, is defined as the least energy
that must be supplied to remove a free electron
from the surface of the metal, against the
attractive forces of surrounding positive ions.
Shown here is a PHOTOCELL. When
incident light of appropriate frequency
strikes the metal (cathode), the light
supplies energy to the electron. The
energy need to remove the electron
from the surface is the WORK!
Not ALL of the energy goes into work!
As you can see the electron then
MOVES across the GAP to the anode
with a certain speed and kinetic
energy.
12. Photoelectric Fact #4
The MAXIMUM KINETIC ENERGY is the energy difference between
the MINIMUM AMOUNT of energy needed (ie. the work function)
and the LIGHT ENERGY of the incident photon.
THE BOTTOM LINE: Energy Conservation must still hold true!
Light Energy, E
WORK done to
remove the electron
The energy NOT used
to do work goes into
KINETIC ENERGY as
the electron LEAVES
the surface.
13. Putting it all together
bmxy
hfKWhfK
hfWK
hfE
+=
−=→−=
=+
=
φ
KINETIC ENERGY can be plotted on the y axis and FREQUENCY on the x-
axis. The WORK FUNCTION is the y – intercept as the THRESHOLD
FREQUNECY is the x intercept. PLANCK‘S CONSTANT is the slope of the
graph.
14. Can we use this idea in a circuit?
We can then use this photoelectric effect idea to
create a circuit using incident light. Of course,
we now realize that the frequency of light must
be of a minimum frequency for this work.
Notice the + and – on the photocell itself. We
recognize this as being a POTENTIAL
DIFFERENCE or Voltage. This difference in
voltage is represented as a GAP that the
electron has to jump so that the circuit works
What is the GAP or POTENTIAL DIFFERENCE is too large?
15. Photoelectric Fact #5 - Stopping Potential
If the voltage is TOO LARGE the electrons WILL NOT have
enough energy to jump the gap. We call this VOLTAGE point
the STOPPING POTENTIAL.
If the voltage exceeds this value, no photons will be emitted no
matter how intense. Therefore it appears that the voltage has
all the control over whether the photon will be emitted and thus
has kinetic energy.
16. Wave-Particle Duality
The results of the photoelectric effect allowed
us to look at light completely different.
First we have Thomas Young’s
Diffraction experiment proving that
light behaved as a WAVE due to
constructive and destructive
interference.
Then we have Max Planck who allowed Einstein to build his
photoelectric effect idea around the concept that light is composed of
PARTICLES called quanta.
17. This led to new questions….
If light is a WAVE and is ALSO a particle, does
that mean ALL MATTER behave as waves?
That was the question that Louis de Broglie
pondered. He used Einstein's famous equation to
answer this question.
18. YOU are a matter WAVE!
Basically all matter could be said to
have a momentum as it moves.
The momentum however is
inversely proportional to the
wavelength. So since your
momentum would be large
normally, your wavelength would
be too small to measure for any
practical purposes.
An electron, however, due to it’s
mass, would have a very small
momentum relative to a person
and thus a large enough
wavelength to measure thus
producing measurable results.
This led us to start using the Electron
Microscopes rather than traditional
Light microscopes.
19. The electron microscope
After the specimen is prepped. It
is blasted by a bean of
electrons. As the incident
electrons strike the surface,
electrons are released from
the surface of the specimen.
The deBroglie wavelength of
these released electrons vary
in wavelength which can then
be converted to a signal by
which a 3D picture can then
be created based on the
signals captured by the
detector.