physics paper 2

• planets in the solar system

  mercury

  venus

  earth

  mars

  jupiter

  saturn

  uranus

  neptune
• smaller planets are mostly made of rock
• larger planets are mostly made of gas
• life cycle of a star (larger)

  nebular

  protostar

  main sequence star

  red super giant

  supernova

  neutron star or black hole
• life cycle of a star(smaller)

  nebular

  protostar

  main sequence star

  red giant

  white dwarf

  black dwarf
• gravitational forces cause the planets to change direction constantly therefore velocity is always changing which means the forces cause the planets to accelerate without increasing the speed
• for stable orbits..


  if the planet moves closer to the sun the gravitational attraction to the sun increases so the orbital speed of the planet increases

  as the force increases so does the acceleration
• how does a nebular turn into a star

  the gravitational attraction draws the particles together and the cloud becomes more concentrated

  this allows fission to occur as the light nuclei fuse to form helium nuclei which produces lots of energy

  the equilibrium forms due to the energy released from fusion that balances with the pressure from the gravitational forces
• when the star collapses (bigger)

  it increases the pressure and temperature so the heavier elements can fuse
• what happens in a supernova

  the star collapses and rebounds on its centre
• what is red shift

  when the light appears red shifted when other galaxies move further away from earth
• as the wavelength is larger the frequency decreases
• red shift is evidence for big bang theory

  shows that the universe is expanding so initially it must have began from a singular point
• CMBR is evidence for big bang theory


  cosmic microwave background radiation

  as the wavelengths were stretched to become microwaves which shows expansion and the big bang theory
• what is wavelength


  the distance between the same point of 2 consecutive waves
• what is amplitude


  the distance from equilibrium line to the crest or the trough
• sound waves can travel through solids by causing vibrations
• if you increase the frequency


  then the velocity increases
• if you increase the wavelength

  the velocity increases
• smaller period= higher frequency = greater velocity
• transverse


  oscillate perpendicular to the waves direction of travel
• longitudinal waves


  oscillate parallel to the waves direction of travel
• reflection


  reflect off a flat surface

  the smoother the surface the stronger the reflection

  rough surfaces scatter light in many different directions

  angle of incidence = angle of reflection
• transmission


  will pass through a transparent material

  the more transparent the more light will pass through
• absorption


  if the frequency of light matches the energy levels of the electrons then they can be absorbed to be remitted as heat

  if there has been a coloured filter over the top then it will absorb all other wavelengths of light so only that colour has been reflected
• EM spectrum


  Radio

  Micro

  infa red

  ultra violet

  x ray

  gamma
• em spectrum waves


  transverse waves

  transfer energy from a source

  speed is constant

  as wavelength decreases frequency increases
• refraction


  when light enters a denser material the waves slow down and it bends towards the normal if it is less dense it bends away from the normal

  different wavelengths refract different amounts which creates the rainbow of colours
• ears and sound waves

  the outer ear collects sound and it moves down the ear canal

  the sound waves hit the eardrum

  the eardrum then vibrates which causes compression in the ear which forces it inwards

  refraction forces in the eardrum vibrates at the same frequency of the sound waves

  the bones act as an amplifying and the fluid transmits signals to the brain
• radio waves


  produced through electrical circuits

  and created alternating current when they are absorbed
• visible light


  specular = smooth surface gives a singular reflection

  diffuse = reflections from a rough surface that causes scattering
• infared 


  the hotter the body is the more radiation in short wavelengths all objects emit and absorb infrared radiation
• black body radiation


  an object which absorbs all the radiation it receives so also emits all the radiation it receives

  at a constant temp = still radiating but absorbing at the same temp

  increasing temp = absorbing more energy than it emits

  cooling = released at a greater rate than it is absorbed
• concave lens


  spreads light outwards

  corrects short sightedness

  virtual

  upright
• convex lens


  focus light inwards

  corrects long sightedness

  real

  inverted
• uses of radio waves


  tv

  radios
• uses of microwaves

  cooking food

  satellites
• uses of infa red

  cooking
• uses of visible light

  fibre optics
• uses of uv


  tanning