Paper 1 COPY Flashcards
how do particles in an ideal gas behave
- gas contains large number of atoms with brownian motion
- volume is negligible when compared to the total volume of the gas
- all collisions are perfectly elastic
*time taken for atoms to collide is negligible compared to the time between collisions - electrostatic forces between atoms are negligble except when colliding
Keplers first law
the orbit of a planet is an ellipse with the sun at one focus. the motion can be modelled as circular
Keplers second law
a line segment joining a planet and the sun sweeps out equal areas during intervals of equal time
Keplers third law
the square of the orbital period is proportional to the cube of the average distance r from the sun
satellites
objects that orbit other larger objects
geostationary satellites
have an orbital period of one day they travel in the same direction as the rotation of the earth along the equatorial plane. therefore remaining above the same point on earth
gravitational potential
work done per unit mass to move an object to that point from infinity
escape velocity
for an object to escape a gravitational field produced by a mass M the kinetic energy of the object at the start must be equal to or greater than the gravitational potential energy required to lift it to infinity.
planet
objects with mass sufficient for their own gravity to force them to take a spherical shape where no nuclear fusion occurs and the object has cleared its orbit of other objects
dwarf planets
plants where the orbit has not been cleared of other objects
asteroids
objects which are too small and uneven in shape to be planets
comets
irregularly sized balls of rock dust and ice. orbit the sun in eccentric elliptical orbits
solar systems
systems conrtaining stars and orbiting objects like planets
galaxies
a collection of stars, dust and gas. Each galaxy contains around 100 billion stars
what are nebulae
gigantic clouds of dust and gas and are the birthplace of all stars
how do stars form?
over years the gravitational attraction between dust and gas particles pulls them together to form clouds. some regions become denser and pull in more dust and gas due to the gravitational collapse. the gravitational energy is converted to thermal energy. the resultant sphere of very hot dense dust and gas is a protostar
what is a protostar
for a start to form the temp and pressure must be high enough for the hydrogen gas nuclei in the protostar to overcome the electrostatic forces of repulsion and undergo nuclear fusion this produces helium nuclei producing a star
what initially happens to a star
remains in stable equilibrium the gravity forces act to compress the star but radiation pressure from photons emitted in fusion and gas pressure within the core counteract this keeping the size constant. this is the main phase of the star
difference between larger stars
they are hotter and undergo fusion faster using up more available hydrogen, therefore have a shorter main phase,
evolution of a low mass star to red giant
0.5m-10m, once hydrogen drops the gravity forces overcome radiation and gas so star begins to collapse inwards, turn into a red giant, the core of the red giant is too cool and the outer shell allows fusion to occur
from red giant to white dwarf
evolved into a white dwarf outer shells drift off as planetary nebula, core remains very dense, has temperature around 3000k no fusion occurs.
what stops white dwarfs collapsing
electron degeneracy pressure (as two electrons cannot exist in the same state)
what is the Chandrasekhar limit
as long as the core mass is below 1.44M the white dwarf star is stable
evolution of a massive star
> 10M, hydrogen depletes helium fusion occurs into heavier elements forming a red supergiant.
what is the red supergiant
has layers of increasingly heavy elements produced from fusion with an inert iron core, the star becomes unstable. a type 2 supernova occurs where there is a shockwave which ejects the materials in the outer shells out in to space and the core collapses
what happens to a collapsed type 2 supernova
elements heavier than iron are formed in supernovas, if the remaining mass is greater than 1.44M, protons and electrons form neutrons. This makes a neutron star, if the mass is greater than 3M the gravitational forces are so strong the escape velocity of the core is greater than the speed of light, this is a black hole.
What are electron levels
bound to an atom can only exist in certain discrete energy levels, each element has its own set of energy levels. when an electron is excited it moves up when it is the opposite it moves towards the down state, releases photon with a specific wavelength
emission line spectra
each element produces a unique emission line spectrum because of the unique set of energy levels associated with its electron
continuous line spectra
all visible wavelengths of light are present produced by heated solid metals
absorption line spectra
dark spectral lines against background of the continuous spectrum with each line corresponding to a wavelength of light used to excite atoms of that element.
diffraction grating
regularly spaced slits that can diffract light, different colours of light have different wavelength have different wavelengths so will be directed at different angles.
dsinx = n(lamda)
Weins law
the black body radiation curve for different temperatures peaks at a wavelength inversely proportional to the temperature of the object. where lamda is the wavelength of light produced with maximum intensity, T is the absolute surface temp
(lamda)(temp) = 2.9x10^-3
stefans law
for a black body, the total radiant heat energy emitted from a surface is proportional to the fourth power of its absolute temperature.
used to relate temp with luminosity
distances
Astronomical Unit = 1.5 x 10^11 average distance from earth to sun
light year = light travels in one year
arc minutes and arcseconds
one degree there are 60 arc minutes and 3600 arc seconds
what is a Parsec
the distance at which a radius of 1 AU subtends an angle of 1 arcsecond in metres, 1 Parsec is 3.1x10^16
what is parallax
can be used to measure the distance to nearby stars, it is the apparent shift in position of an object against a backdrop of distance objects that dont appear to move accurate up to 100pc
cosmological principle
the universe is isotropic (same in all directions no centre or edge) and homogenous, and the laws of physics are universal.
doppler effect
apparent shift in wavelength occurring when the source of the waves is moving. if moving to detector wavelength appears to decrease, otherwise contrary
Doppler effect in starlight
shifts the position of spectral lines, can be used to determine relative speed of a star
∆wavelength/wavelength = v/c
Hubbles law
recessional velocity of a galaxy is proportional to its distance from earth, further away the star the faster it is moving away from us V = Hd
universes expanding Hubbles law
all light from distant galaxies are red shifted showing they are moving away from earth fabric of space time expanding
Big Bang theory evidence
all objects were initially contained in a singularity which suddenly expanded outwards.
- microwave background radiation
originally high energy gamma photons were distributed across the universe
evolution of universe
10^-35 s = universe expands rapidly with accerlation known as inflation. no matter only high energy gamma photons and em radiation
10^-6 s =first fundamental particles gain mass
10^-3 s =most mass is created using pair production hadrons come from quarks
1s = production of mass halted
dark energy
used to explain the accelerating expansion and should make up 68% of the total energy in the universe
