Transcript File

14 Lecture in physics
Revision
Missed topics
Higgs boson
Big Bang
Wrong physics scores for telematics students
Proof of R = 2F for spherical mirror.
Black-Body radiation problem
Boltzmann law
The Stefan–Boltzmann law, also known as
Stefan's law, describes the power radiated from
a black body in terms of its temperature.
Specifically, the Stefan–Boltzmann law states
that the total energy radiated per unit surface
area of a black body across all wavelengths per
unit time (also known as the black-body radiant
exitance or emissive power), j*, is directly
proportional to the fourth power of the black
body's thermodynamic temperature T
Rayleigh–Jeans law
In physics, the Rayleigh–Jeans law attempts to
describe the spectral radiance of
electromagnetic radiation at all wavelengths
from a black body at a given temperature
through classical arguments.
Wien's displacement law
Wien's displacement law states that the black body
radiation curve for different temperatures peaks at a
wavelength inversely proportional to the temperature.
The shift of that peak is a direct consequence of the
Planck radiation law which describes the spectral
brightness of black body radiation as a function of
wavelength at any given temperature. However it had
been discovered by Wilhelm Wien several years before
Max Planck developed that more general equation, and
describes the entire shift of the spectrum of black body
radiation toward shorter wavelengths as temperature
increases.
Matter wave
All matter can exhibit wave-like behaviour. For
example a beam of electrons can be diffracted just
like a beam of light or a water wave. Matter waves
are a central part of the theory of quantum
mechanics, an example of wave–particle duality.
The concept that matter behaves like a wave is also
referred to as the de Broglie hypothesis (/dəˈbrɔɪ/)
due to having been proposed by Louis de Broglie in
1924. Matter waves are often referred to as de
Broglie waves.
Eigenvalues
Missed astrophysics problems
Revision for the Final Exam
Quantum physics
Pauli exclusion principle
Quantum entanglement
Superposition (configurations interaction,
interference, resulting diffraction)
Elementary particles
Higgs boson
gives mass
Astrophysics
Supernovae
Supernova
A supernova is a stellar explosion that briefly outshines
an entire galaxy, radiating as much energy as the Sun or
any ordinary star is expected to emit over its entire life
span, before fading from view over several weeks or
months. The extremely luminous burst of radiation expels
much or all of a star's material at a velocity of up to
30,000 km/s (10% of the speed of light), driving a shock
wave into the surrounding interstellar medium. This
shock wave sweeps up an expanding shell of gas and dust
called a supernova remnant. A great proportion of
primary cosmic rays comes from supernovae.
Supernova (continued)
• Supernovae are more energetic than a nova.
Nova means "new" in Latin, referring to what
appears to be a very bright new star shining in
the celestial sphere; the prefix "super-"
distinguishes supernovae from ordinary novae
which are far less luminous. The word supernova
was coined by Walter Baade and Fritz Zwicky in
1931. It is pronounced /ˌsuːpəˈnoʊvə/ with the
plural supernovae /ˌsuːpəˈnoʊviː/ or supernovas
(abbreviated SN, plural SNe after "supernovae").
Supernova (continued)
Supernovae can be triggered in one of two ways: by the
sudden reignition of nuclear fusion in a degenerate star;
or by the gravitational collapse of the core of a massive
star. In the first case, a degenerate white dwarf may
accumulate sufficient material from a companion, either
through accretion or via a merger, to raise its core
temperature, ignite carbon fusion, and trigger runaway
nuclear fusion, completely disrupting the star. In the
second case, the core of a massive star may undergo
sudden gravitational collapse, releasing gravitational
potential energy that can create a supernova explosion.
Supernova (continued)
The last directly observed supernova in the Milky
Way was Kepler's Star of 1604 (SN 1604); remnants
of two more recent supernovae have been found
retrospectively. Nevertheless, observations in other
galaxies indicate that supernovae occur on average
about three times every century in the Milky Way.
They play a significant role in enriching the
interstellar medium with higher mass elements.
Furthermore, the expanding shock waves from
supernova explosions can trigger the formation of
new stars.
Big Bang
Big Bang
• The Big Bang theory is the prevailing cosmological model for the
birth of the universe. The model postulates that at some moment
all of space was contained in a single point from which the universe
has been expanding ever since. Modern measurements place this
moment at approximately 13.8 billion years ago, which is thus
considered the age of the universe. After the initial expansion, the
universe cooled sufficiently to allow the formation of subatomic
particles, and later simple atoms. Giant clouds of these primordial
elements later coalesced through gravity to form stars and galaxies.
The Big Bang theory does not provide any explanation for the initial
conditions of the universe; rather, it describes and explains the
general evolution of the universe going forward from that point on.
Big Bang (continued)
Since Georges Lemaître first noted, in 1927, that an expanding
universe might be traced back in time to an originating single point,
scientists have built on his idea of cosmic expansion. While the
scientific community was once divided between supporters of two
different expanding universe theories—the Big Bang and the Steady
State theory, accumulated empirical evidence provides strong support
for the former. In 1929, Edwin Hubble discovered indications that all
galaxies are drifting apart at high speeds. In 1964, the cosmic
microwave background radiation was discovered, which was crucial
evidence in favor of the Big Bang model, since that theory predicted
the existence of background radiation throughout the universe before
it was discovered. The known physical laws of nature can be used to
calculate the characteristics of the universe in detail back in time to an
initial state of extreme density and temperature.
Aliens