Physics Paper 3

• Red Shift


  Shift of an objects wavelength towards the red end of the spectrum due to the object moving away from earth.
• What is red-shift evidence for?

  Expansion of the universe
• blue shift


  Shift of the objects wavelength towards the blue end of the spectrum due to object moving towards the earth.
• absolute magnitude


  Magnitude of a star as it appears if placed 10 parsecs from earth
• astronomical unit


  the average distance between the centre of the earth and the centre of the sun
• Apparent magnitude


  the magnitude of a star as it appears to an observer on the earth.
• Big Bang Theory


  Theory that the earth originated as a small, dense and hot region that expanded and cooled forming the universe
• Black body radiation


  Perfect absorber and emitter of all possible wavelengths of light
• Binary star system


  Two stars orbiting their common center of gravity.
• Black hole


  Region with an escape velocity > speed of light
• How are black holes formed?


  1. Mass is so dense neutrons form into other neutrons. Mass tends to a singular point.
• Size of star that forms a black hole

  >3 Msol
• Mass of core that will form a neutron star

  >1.4 Msol
• Chandrasekhar limit


  the upper limit to the mass of a white dwarf (<1.4 Msol)
• How can black holes be observed?


  1. Material falling into the black hole

  2. Stars orbiting an invisible centre of mass
• Charged-Coupled device (CCD)


  Use the photoelectric effect to convert light into digital information.
• What are CCD's made of

  - Silicone chips divided into pixels.

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• Potential Wells (CCDs)


  Electrons get trapped in potential wells causing a potential difference identical to the image produced.
• Chromatic Aberration


  Different focal lengths of different wavelengths of light lead to colours being focused at different points
• Collecting power


  Measure of ability of lens/mirror to collect em radiation
• Collecting power equation


  Collecting power = Area of lens/mirrors
• Concave/ diverging lens


  Light spreads out
• Convex/ converging lens


  Light focuses in
• Doppler Effect


  Apparent change in frequency of a wave caused by the relative motion between the source of a wave and an observer
• Event horizon


  Boundary of black hole where escape velocity = speed of light
• Exoplanet


  Planets not part our solar system and orbit other starts
• Eyepiece


  Magnifies the image produced by the objective lens
• Objective


  Collects light to form a real image
• Focal length


  Distance between centre of lens and principal focus
• Hipparcos scale


  Classification of objects by their apparent magnitude
• Hipparcos scale- Brightest star

  1
• Hipparcos scale- dullest star

  6
• How many times greater is a magnitude 1 star compare to a magnitude 6 star?

  100
• Hubbles Law


  Speed of galaxy moving away from ours is proportional to distance away from us
• Intensity


  Power received from a star per unit area
• Light year (ly)


  Distance than an EM wave travels in a year (In a vacuum)
• Long-lived Gamma ray bursts


  Bursts of gamma lasting between 10 and 100 seconds. In a type 2 supernova
• Magnifying power/ Angular Magnification


  Angle made by the image from eyepiece : angle made by object with the unaided eye
• Normal adjestment


  Distance between the object and eyepiece in a refracting telescope us = sum of focal length
• Parallax


  Apparent change of position of a nearer star in comparison to distant stars in the background as a result of the earths orbit