A-Level Physics Specification

AQA 7408

Section 9.3: Cosmology

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#9.3.1

Doppler effect

\(\dfrac{∆f}{f} = \dfrac{v}{c} \) and \(z = \dfrac{∆λ}{λ} = -\dfrac{v}{c} \) for \(v≪c\) applied to optical and radio frequencies.

Calculations on binary stars viewed in the plane of orbit.

Galaxies and quasars.

#9.3.2

Hubble's law

Red shift \(v = Hd \)

Simple interpretation as expansion of universe; estimation of age of universe, assuming H is constant.

Qualitative treatment of Big Bang theory including evidence from cosmological microwave background radiation, and relative abundance of hydrogen and helium.

#9.3.3

Quasars

Quasars as the most distant measurable objects.

Discovery of quasars as bright radio sources.

Quasars show large optical red shifts; estimation involving distance and power output.

Formation of quasars from active supermassive black holes.

#9.3.4

Detection of exoplanets

Difficulties in the direct detection of exoplanets.

Detection techniques will be limited to variation in Doppler shift (radial velocity method) and the transit method.

Typical light curve.