Things To Remember Paper 1 Based MARKSCHEME definitions

Question 1

What is a whit dwarf

Answer 1

The remnant core of a red giant after its shed its outer layers

Question 2

Explain how parallax is used to find distances of stars (3 marks)

JUST LEARN

Answer 2

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

Question 3

Why is hydrigen spectral lines used to measure velocities of stars? (2 marks)

Answer 3

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

Question 4

HUBBLES law defitmion

Answer 4

The recessional speed of a galaxy is proportional to the distance away from us

Question 5

Why does Hubble law break down for close ?

IMPORTSNT wording

Answer 5

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 )

Question 6

Why do extremely distant stars not fit HUBBLES law too?

Answer 6

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

Question 7

Definiton of an energy level / electron shell

Answer 7

Discrete/ quantised energy of an electron ( at that position )allowed in an atom

Question 8

Why can’t we use HUBBLES law to explain a binary star in our own galaxy?

Answer 8

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)

Question 9

Features of CMBR (2)

Answer 9

• 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

Question 10

What does intensity mean

Answer 10

Power emitted per unit area

Question 11

Actual definition for what was the Big Bang

Answer 11

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

Question 12

CMBR explanation with Big Bang (3 points)

Answer 12

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

Question 13

Why is hydrogen used for identifying velocities in galaxy

Answer 13

Is the most abundant element

Also produces the most intense spectral lines for mesudrment

Question 14

What is kinetic model basic (2)

What is Brownian motion (2 marks)

How does brownian prove

Answer 14

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

Question 15

How to observe Brownian motion in a lab

Answer 15

• 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

Question 16

Resonance definition

Answer 16

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

Question 17

Internal energy definition

Answer 17

Total sum of potential and kinetic energy of the ATOMS / MOLECULES OF A SUBSTANCE

Question 18

Principle of moments

Answer 18

When object is in EQUILBKRUM sum of anti = sum of clockwise

Must say EQUILBKRUM

Question 19

What do everythign at same temp have

Answer 19

Same AVERAGE KE

Question 20

How does water motion arrangement solid motion are magnet

Answer 20

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

Question 21

What does homigenous defintion mean

Answer 21

Uniform DISTRUBTION of matte

Question 22

Gravational potential defintion

Answer 22

Work done per unit mass in bringing object from infinity to a certain point away from a gravational field

Question 23

Black hole characteristics all answers

Answer 23

• grav field so string escape velocity greater than speed of light
• very dense / singularity
• disrupts space time SIGNIFICANTLY
• does not emit any visible light

Question 24

Evolution of universe mark scheme summarised

When is t =1?

Answer 24

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

Question 25

Lumniosity

Answer 25

Total radiant power of a star

Question 26

How is an absorbtion spectrum from a star made

Answer 26

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

Question 27

When is there maximum normal / maximum centripetal force on circular motion ( what ck dito n)

Answer 27

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

Question 28

4 ideal gas , kinetic theory

Answer 28

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

Question 29

Remember how to use kinetic theory to explain how gas exerts a force with Newtown

Answer 29

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

Question 30

General how to twke measurements accurately

Answer 30

Avoid parallax Average in different places

Question 31

Remember what happens when dampened ampltiude vs driving frewuency graph 3 points, especially last

Answer 31

1) all amplitudes lower 2) peak amplitude occurs lower f then natural f 3) THE PEAK IS WIDER TOO

Question 32

Rememebr where does maximum damoenign FIRCE and reduction in energy occur

Answer 32

At equilbirum as max v, and the first one too as that has max v

Question 33

How does lumniosity snd mass lost of star link

Answer 33

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!