Things To Remember Paper 1 Based MARKSCHEME definitions Flashcards
What is a whit dwarf
The remnant core of a red giant after its shed its outer layers
Explain how parallax is used to find distances of stars (3 marks)
JUST LEARN
1) parallax is the apparent displacement of a nearby star relative to the position of more distant stars
2) this is observed due to the earth orbiting around the sun
3) after measuring the parallax angle, an angle of 1 arcsecond subtending a distance of 1 AU from earth corresponds to a distance 1 pc
Why is hydrigen spectral lines used to measure velocities of stars? (2 marks)
1) hydrogen is rhe most common element in stars
2) hydrogen produces the most intense spectral lines, and so other elements intensity of lines may be too low to measure
HUBBLES law defitmion
The recessional speed of a galaxy is proportional to the distance away from us
Why does Hubble law break down for close ?
IMPORTSNT wording
Nearby : galaxies are attracted to us due to strong gravitational attraction, so this affects their motion and thus don’t fit HUBBLES law
(. NOT ALL OF THE, ARE COMING TOWARDS US , BUT EVEN THOSE ONES That are moving away TO US HAS THEIR MOTION CHANGED SO THST THEY DONT FIT IN WITH HUBBLES LAW )
(This applies the most the galaxies and stars COMPLETLEY moving towards us )
Why do extremely distant stars not fit HUBBLES law too?
The rate of expansion of the universe is ACCELERATING, as shown by the need for dark energy, and thus for really distant galaxies the velocity is so much for its distance that it doesn’t follow HUBBLES law anymore
Definiton of an energy level / electron shell
Discrete/ quantised energy of an electron ( at that position )allowed in an atom
Why can’t we use HUBBLES law to explain a binary star in our own galaxy?
Because HUBBLES law applies to GALAXIES, not a star in our OWN GALAXY
( although might follow trend, the actual law and constant is defined for galaxy speed)
Features of CMBR (2)
- the intensity of microwaves is the same in all directions
- ## correspond to a temperature of 2.7k, which is thr temperature of the universe when modelled as black body
What does intensity mean
Power emitted per unit area
Actual definition for what was the Big Bang
1) the explanation for the creation an evolution of the universe
2) which stated universe was a singularity of infinitely hot and dense at the start and has expanded and cooled since
CMBR explanation with Big Bang (3 points)
The Big Bang explains CMBR :
1) early universe was concentrated with high energy gamma photons at high temperatures
2) as universe expanded and cooled , the wavelength of gamma photons red shifted / stretched to microwaves
3) we now observe these as microwave background radiation
4) the TEMPERTAURE of these microwaves corresponds to a temperature of 2.7k which is the temperature of the universe
Why is hydrogen used for identifying velocities in galaxy
Is the most abundant element
Also produces the most intense spectral lines for mesudrment
What is kinetic model basic (2)
What is Brownian motion (2 marks)
How does brownian prove
Kinetic model = that matter is made form particles with ke
Brownian motion = haphazard / random movement of particles when suspended in a fluid due to collisions with surrounding fluid particles, giving them random velocities ( and thus ke)
Bro ain motion shows matter to be made from particles and have me = thud proved kinetic model
How to observe Brownian motion in a lab
- use a smoke cell, observed under a microscope
- the smoke particles are big enough to be seen under a microscope
- the smoke will scatter light and show as jittery movements of random directions and velocities
The reason for this is that they are collidjg with invisible air particles
Resonance definition
When the frequency of the driving force matches (or nears) the natural frequency of the system
At this point maximum energy transfer occurs , thus maximum amplitude is achieved
Internal energy definition
Total sum of potential and kinetic energy of the ATOMS / MOLECULES OF A SUBSTANCE
Principle of moments
When object is in EQUILBKRUM sum of anti = sum of clockwise
Must say EQUILBKRUM
What do everythign at same temp have
Same AVERAGE KE
How does water motion arrangement solid motion are magnet
Water motion
- random, translational , and flows
- arrangement irregular
Solid
- vibrates about fixed position shm
Arrangement = regular lattice
When heated, moves with higher ke, so higher velocities, higher amplitudes in vibration, more spacing
What does homigenous defintion mean
Uniform DISTRUBTION of matte
Gravational potential defintion
Work done per unit mass in bringing object from infinity to a certain point away from a gravational field
Black hole characteristics all answers
- grav field so string escape velocity greater than speed of light
- very dense / singularity
- disrupts space time SIGNIFICANTLY
- does not emit any visible light
Evolution of universe mark scheme summarised
When is t =1?
1) t = 0 singularity infinitely hot and dense
2) rapid acceleration = inflation, conc with gamma photons and NO MASS
3) then first fundamental gain mass ( quarks and lepton) rest pair production
4) then quarks combine to make hadrons (protons neutrons )
- t = 1 matter stops ( AFTER HADRONS)
5) and these combine to make heliumb deuterium nuclei
6 ) 380K ATOMS capture nuclei and cmbr is there
Lumniosity
Total radiant power of a star
How is an absorbtion spectrum from a star made
1) star emits light of CONTINOUS spectrum
2) photons from this are absorbed by electrons of cooler gas atoms surrounding stars
3) where the energy of the photons match the energy difference between levels, electrons will excite, this must be the EXACT DIFFERENCE
4) eventually the electrons will de excite and re emit electrons, however the intensity of these in original direction will be low now as emit in all directions
5) so observed from earth, we see a CONTINOUS spectrum with black lines for missing frewuencies of photons that were absorbed by cooler gas atoms. Therefore see a Continous spectrum
When is there maximum normal / maximum centripetal force on circular motion ( what ck dito n)
Max Fc at top when NORMAL = 0 ( so speed must be fast enough such that normal is 0, and this is lowest normal can be and still in contact)
Max normal is at bottom as Fc=N -W, N = Fc + W
4 ideal gas , kinetic theory
1) gas molecules move with random motion and velocity
2) Collisons with each other and container elastic
3) Negligible time spent colliding compared to time spent without colliding
4) electrostatic forces between the gases are negkible EXCEPT WHEN COLLIDJG. ( hence potential energy is 0)
5) volume of gas is negligible compared to volume of empty space
Remember how to use kinetic theory to explain how gas exerts a force with Newtown
Gases collide with each other and contianers leading to a change of momentum in a given time , as Collisons are ELASTIC this is = to …, by Newton 2nd law it exerts a force
Due to Newton’s third law , the gas molecule will exert same force on the contianier
Total / area = pressure
General how to twke measurements accurately
Avoid parallax
Average in different places
Remember what happens when dampened ampltiude vs driving frewuency graph
3 points, especially last
1) all amplitudes lower
2) peak amplitude occurs lower f then natural f
3) THE PEAK IS WIDER TOO
Rememebr where does maximum damoenign FIRCE and reduction in energy occur
At equilbirum as max v, and the first one too as that has max v
How does lumniosity snd mass lost of star link
Higher lumniosity means higher loss if mass. The mass they are talking about is the MASS OD HYDROGEN, because the mass of this DISSAPPEARS with fusion
So higher Mass loss, means more fusion hydrogen etc the same, so run out of fuel quicker = lower lifecycle!
