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OCR A LEVEL PHYSICS ASTROPHYSICS
QUIZ WITH VERIFIED ANSWERS
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What is the typical mass of a stellar core that creates a black hole? - CorreCt
Answers -3 solar masses
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What is the Luminosity of a star? - CorreCt Answers -The total radiant
power output of a star (Energy radiated per second)
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What is a black body spectrum? - CorreCt Answers -The characteristic
spectrum of radiation emitted by all black bodies in thermal equilibriun
with their surroundings
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What is Stefan's Law - CorreCt Answers -The total power emitted per unit
surface area by a black body is proportional to the 4th power of the absolute
temperature

What are electron energy levels in an atom? - CorreCt Answers -Discrete
energy levels within an atom in which electrons can exist
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What is the excited state of an atom? - CorreCt Answers -An atom in which
electrons have been raised to an energy level above the ground state
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What is meant by a discrete quantity? - CorreCt Answers -Occuring only at
particular values (as opposed to continous)

What is a diffraction grating? - CorreCt Answers -A large number of closely
spaced alternating transparent and opaque 'lines' used as a tool to produce
spectra via interference
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What occurs in excitation of an atom? - CorreCt Answers -The atom gains
energy and an electron moves up to a higher energy level
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What occurs during de-excitation of an atom? - CorreCt Answers -An
excited electron drops down energy levels and emits a photon
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What determines the frequency of photons that can be absorbed or emitted
by an atom? - CorreCt Answers -The energy of the photon must be equal to
a gap between energy levels
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What is the effect of reducing the spacing of slits in a diffraction grating? CorreCt Answers -It increases the angles of each maximum
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What is an astronomical unit (AU)? - CorreCt Answers -The average
distance from Earth to the Sun

What is a light year? - CorreCt Answers -The distance that light travels in a
vacuum in one year
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What is the maximum distance that can be measured by parallax? - CorreCt
Answers -100 parsecs

What is the parallax angle of a star? - CorreCt Answers -Half the angular
shift observed in the apparent position of a nearby star from Earth over a
period of six months
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What is p in the equation d = 1/p ? - CorreCt Answers -Parallax angle of a
nearby star in arcseconds
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How is the red/blue shift of a galaxy measured? - CorreCt Answers -The
absorption spectrum of the galaxy is compared to those of elements
observed on the Earth
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What is red shift? - CorreCt Answers -The shift towards longer wavelengths
of absorption lines of a galaxy moving away from the Earth
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What is Hubble's Law? - CorreCt Answers -The recessional speed of distant
galaxies is approximately proportional to their distance from us

What is the cosmological principle? - CorreCt Answers -The idea that the
universe is homogenous and isotropic on a large scale and that the laws of
physics are the same everywhere in the Universe
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- CorreCt
Answers -The idea that matter (on a large scale) is distributed uniformly
across the universe, which therfore has approximately constant density
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What is the Big Bang? - CorreCt Answers -The leading theory to describe
the origin of the Universe in which space and time expanded from a
singularity approximately 13
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What is Cosmic Microwave Background Radiation (CMBR)? - CorreCt
Answers -The largely uniform microwave radiation with the blackbody
spectrum of an object at 2
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How does the the Big Bang theory explain the Cosmic Microwave
Background Radiation (CMBR)? - CorreCt Answers -When it was young the
Universe was very hot and filled with short wavelength photons
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How can Hubble constant be determined? - CorreCt Answers -The gradient
of the best-fit line for a plot of recessional speed (y-axis) vs distance (x-axis)

How can the age of the Universe be estimated using the Hubble Constant? CorreCt Answers -age of the Universe = 1 / Hubble constant

Approximately what percentage of the Universe is thought to be comprosed
of normal matter? - CorreCt Answers -5%

Approximately what percentage of the Universe is thought to be composed
of dark matter? - CorreCt Answers -27%

Approximately what percentage of the Universe is thought to be composed
of dark energy? - CorreCt Answers -68%

What is (Cosmic) inflation? - CorreCt Answers -A period very early on
(10⁻³⁵ - 10⁻³⁰s) in the evolution of the universe during which an unknown
mechanism appears to have caused a very rapid expansion of the universe
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What was the composition of the early Universe after fusion ended at
around 100s
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Why was light able to freely propagate in the Universe from around
380,000 years? - CorreCt Answers -Nuclei captured electrons forming
neutral atoms
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What is the universe? - CorreCt Answers -Everything that exists
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What is nuclear fusion? - CorreCt Answers -The fusing of light nuclei to
produce heavier nuclei releasing energy in the process
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What prevents gravity from causing stars to collapse? - CorreCt Answers The radiation and gas pressure pushing outward
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What is radiation pressure in a star? - CorreCt Answers -Pressure from the
photons created by fusion in the core of a star
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What is a main sequence star? - CorreCt Answers -A stable star fusing
hydrogen in helium
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What is a Red Giant? - CorreCt Answers -The stage after the main sequence
for a star with insufficient mass to go supernova
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- CorreCt Answers -An inert core
surronded by shells fusing elements heavier then Hydrogen
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What is the Chandrasekhar limit? - CorreCt Answers -The mass of a star's
core below which the star will form a white dwarf
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What is a red supergiant? - CorreCt Answers -A huge star in the last stages
of its life prior to undergoing a supernova explosion
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What is a neutron star? - CorreCt Answers -The extremely dense remnant
core of a red supergiant star made almost entirely of neutrons
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What evidence suggests the expansion of the Universe is accelerating? CorreCt Answers -Light from very distant type 1a supernova are less
intense than predicted
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