Astrophysics Definitions 4.0 / 5 based on 2 ratings ? PhysicsAstrophysicsLenses and opticsA2/A-levelAQA Created by: natfarmer97Created on: 06-05-15 12:00 Doppler Effect Change in a wave's wavelength caused by the motion of its source 1 of 15 The Astronomical Unit Mean distance between the Earth and the Sun 2 of 15 Main Sequence Stars Stars that are producing helium in their core 3 of 15 Grazing Telescopes Astronomical device for detecting X-Rays 4 of 15 Focal Length Distance between the lens axis and the principal focus 5 of 15 Resolving Power Smallest angle where two points can be distinguished 6 of 15 Black Body A body that absorbs all wavelengths of electromagnetic radiation and cam emit all wavelengths of electromagnetic radiation 7 of 15 Redshift The characteristic spectral lines of the elements are all at a longer wavelength than you would expect 8 of 15 The Hot Big Bang Theory The universe started off very hot and very dense and has been expanding ever since 9 of 15 The Cosmological Principal The Universe is homogeneous and isotropic so it doesn't have a centre 10 of 15 Homogeneous Every part is the same as every other part 11 of 15 Isotropic Everything looks the same in every direction 12 of 15 Relative Magnitude A measure of how bright a star appears to us 13 of 15 Absolute Magnitude The relative magnitude of a star when viewed from a location 10 parsec from Earth 14 of 15 Airy Disc The bright central spot in the system of diffraction rings formed by an optical system with light from a point source 15 of 15
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