5.5.1
Stars |
(a) the terms planets, planetary satellites, comets, solar systems, galaxies and the universe |
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(b) formation of a star from interstellar dust and gas in terms of gravitational collapse, fusion of hydrogen into helium, radiation and gas pressure |
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Learners are not expected to know the details of fusion in terms of Einstein's mass-energy equation. |
(c) evolution of a low-mass star like our Sun into a red giant and white dwarf; planetary nebula |
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| (d) characteristics of a white dwarf;
electron degeneracy pressure;
Chandrasekhar limit |
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(e) evolution of a massive star into a red super giant and then either a neutron star or black hole;
supernova |
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| (f) characteristics of a neutron star and a black hole |
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(g) Hertzsprung–Russell (HR) diagram as luminosity-temperature plot;
main sequence; red giants; super red giants; white dwarfs. |
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5.5.2
Electromagnetic radiation from stars |
(a) energy levels of electrons in isolated gas atoms |
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(b) the idea that energy levels have negative values |
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| (c) emission spectral lines from hot gases in terms of emission of photons and transition of electrons between discrete energy levels |
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| (d) the equations
hf= ΔE and
hc/λ = ΔE |
hf= ΔE
hc/λ = ΔE |
Learners will also require knowledge of section 4.5 |
(e) different atoms have different spectral lines which |
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(f) continuous spectrum, emission line spectrum and absorption line spectrum |
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(g) transmission diffraction grating used to determine the wavelength of light. |
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The structure and use of an optical spectrometer are not required; |
(h) the condition for maxima
d sin θ = nλ
where d is the grating spacing . |
d sin θ = nλ |
Proof of this equation is not required |
(i) use of Wien's displacement law
λmax∝1/T
to estimate the peak surface temperature (of a star) |
λmax∝1/T |
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(j) luminosity L of a star;
Stefan's law
L = 4πr2σT4
where σ is the Stefan constant |
L = 4πr2σT4 |
Learners will also require knowledge of 4.4.1 |
(k) use of Wien's displacement law and Stefan's law to estimate the radius of a star. |
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5.5.3
Cosmology |
(a) distances measured in astronomical unit (AU), light-year (ly) and parsec (pc) |
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| (b) stellar parallax; distances the parsec (pc) |
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(c) the equation
p = 1/d
where p is the parallax in seconds of arc and d is the distance in parsec |
p = 1/d |
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(d) the Cosmological principle;
universe is homogeneous, isotropic and the laws of physics are universal |
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| (e) Doppler effect;
Doppler shift of electromagnetic radiation |
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(f) Doppler equation
Δλ/λ ≈ Δf/f ≈ v/c
for a source of electromagnetic radiation moving relative to an observer |
Δλ/λ ≈ Δf/f ≈ v/c |
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(g) Hubble's law;
v ≈ H0d
for receding galaxies, where H0 is the Hubble constant |
v ≈ H0d |
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(h) model of an expanding universe supported by galactic red shift |
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| (i) Hubble constant H0 in both km s–1 Mpc–1 and s–1 units |
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(j) the Big Bang theory |
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(k) experimental evidence for the Big Bang theory from microwave background radiation at a temperature of 2.7 K
The development and acceptance of Big Bang theory by the scientific community |
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| (l) the idea that the Big Bang gave rise to the expansion of space-time |
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(m) estimation for the age of the universe; t ≈ H0–1 |
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| (n) evolution of the universe after the Big Bang to the present |
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(o) current ideas;
universe is made up of dark energy, dark matter, and a small percentage of ordinary matter. |
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