Particle Interactions
Heisenberg Uncertainty Principle
According to Heisenberg, measurements
of the energy of a particle or of an energy
th
level are subject to an uncertainty
This uncertainty is not the result of random
or systematic errors but result
Cosmology
A long time ago
Shortly after the big bang (10-34s) the
temperature of the universe was of the
order of 1023K
The current temperature today is only 2.7K
Called cosmic microwave background
radiation (CMB radiation)
1
CMB Radiation
CMB radiati
Experimental Evidence for the
Standard Model
Murray Gell-Mann
Proposed the theory
of quarks
Predicted the
existence and mass
of a new particle, The subsequent
discovery at
Brookhaven National
Laboratory lent major
support to the idea of
quarks
1
Direct
String Theory
Gravitational Interaction
The strength of the gravitational interaction
is very small and therefore is irrelevant
(and is ignored) for subatomic physics
However, at very large energies
gravitation becomes comparable to the
other forces and
Particle Physics
The stuff that things are made of
Elementary Particle
A particle with no internal structure
Not made out of smaller constituents
Electrons are elementary particles
The Search for Truth
By the mid 1930s it was recognized that
atoms wer
Detectors and Accelerators
The Need for High Energies
The electromagnetic interaction allows for
the following process
e+ + e- particle + antiparticle
An electron and positron collide, annihilate
each other producing a virtual photon
which rematerializ
Quantum Physics
The Photoelectric Effect
1887, Heinrich Hertz
Conducting experiments to test the
electromagnetic theory of light
Certain metals produce an electric current
when exposed to light of very short
wavelength
Called the photoelectric effect
Quantum Theory
Atomic Spectra
The emission and absorption spectra has
lines at specific wavelengths for a given
gas
Johann Balmer (1885) discovered, by trial
and error, that the wavelengths of the
emission spectrum of Hydrogen were
given by:
1 1
= R 2
Quantum Physics
Review Worksheet Answers
1.
2.
3.
4.
5.
6.
B
A
C
B
B
A
7.
(a)
any particle has wave-like properties / other appropriate statement;
where wavelength =
h
with h and p identified;
p
Can be back credited from (b).
(b)
use of E =
p2
;
2m
OR
1
2
Relative Motion
Relative Motion
All motion, and even time, is relative to an
observer.
A person that is walking forward at 4km/h on a
ship will be seen as moving faster by an observer
on the shore.
This occurs because the speed of the ship is
added to
Resistors in Series and in
Parallel
Series
Voltage drop is different across each
resistor
The total voltage drop across the circuit is
equal to the sum of the voltage drops
across the individual resistors
Current is the same through each resistor
Serie
Power,
E.M.F.,
and
Internal Resistance
Power
Power is defined as the rate at which
energy is used by or supplied to the circuit.
Power is dissipated in resistors (as heat)
P
W qV
W
t
and
q It
W ItV
or
W
IV
t
P IV
V IR
P I 2R
P
V2
R
1
E.M.F.
(Electromot
Electric Currents
Current
A moving charge creates an electric
current.
Electric current is the amount of charge
that moves through the cross-sectional
area of a wire per unit interval of time.
I
q
t
Unit: Ampere, Amp (A)
Electric Currents
In a conducto
Name: Date:
Power
Part 1: Concepts:
1. Take a sampling of a few of the objects that are used on a daily basis and complete the chart
given below
Part 2: Practice Problems: mg @dlfa (Mg; ; /{3 9:
' 2. A basement light has a power of 75 W. How mu
Resistors in Series and in
Parallel
Series
Voltage drop is different across each
resistor
The total voltage drop across the circuit is
equal to the sum of the voltage drops
th
th
across the individual resistors
Current is the same through each resistor
Induced E.M.F.
Induced EMF
Faraday showed that moving a wire in a
magnetic field induces a current in that
wire.
As work is done in moving the charge from
one end to the other, an electric potential
exists: induced emf (voltage)
1
The induced emf (and
Alternating Current
Alternating Current
The most important application of the laws
of electromagnetic induction was the
development of the electric generator.
1
The magnitude of the emf and current
varies with time
Maximum when coil is perpendicular to
Sensors in Potential Divider
Circuits
Light-Dependent Resistor (LDR)
Photoresistor, photoconductive cell
An electronic component whose
resistance decreases with increasing
incident light intensity.
1
Most are made with CdS
Found in many consumer items
Power,
E.M.F.,
and
Internal Resistance
Power
Power is defined as the rate at which
energy is used by or supplied to the circuit.
Power is dissipated in resistors (as heat)
1
P=
W = qV
W
t
and
q = It
W = ItV
or
W
= IV
t
P = IV
V = IR
2
P=I R
or
V2
P=
R
E
Electrostatics
Static Electricity; Electric Charge and Its Conservation
The word electricity comes from the Greek work elektron, which means amber. Amber is
petrified tree resin, and the ancients knew that if you rub an amber rod with a piece of cloth, th
Impulse
Impulse
In a collision of two ordinary objects, both
objects are deformed, often considerably,
due to the large forces involved.
1
When the collision occurs, the force usually
jumps from zero at the moment of contact to
a very large value within
Momentum
Momentum
Momentum is defined as the mass of an
object times its velocity.
p = mv
1
Newtons Second Law (again)
To change the momentum of an object, we need
a force.
Newtons second law of motion applies
Newton originally said The ratio of chang
Projectile Motion
Horizontal Motion
What would happen if we shot a cannon
ball at velocity, v, horizontally in a world
without gravity?
It would travel horizontally with constant
velocity, v
1
Vertical Motion
What would happen if we dropped a
cannon ba