**Astrophysics and Cosmology**

## Specification:126 use the expression
F = Gm1m2/r^2127 derive and use the expression g = -Gm/r^2 for the gravitational field due to a point mass128 recall similarities and differences between electric and gravitational fields 129 recognise and use the expression relating flux, luminosity and distance F = L/(4πd^2) application to standard candles130 explain how distances can be determined using trigonometric parallax and by measurements on radiation flux received from objects of known luminosity (standard candles) 131 recognise and use a simple Hertzsprung-Russell diagram to relate luminosity and temperature. Use this diagram to explain the life cycle of stars 132 recognise and use the expression = σL T^4 x surface area, for black body radiators (for a sphere L = 4πr2σT4) (Stefan-Boltzmann law) 133 recognise and use the expression: λ maxT = 2.898 x 10^-3 m K (Wien’s law) for black body radiators134 recognise and use the expressions z = Δλ /λ ≈ Δf/f ≈ v/c for a source of electromagnetic radiation moving relative to an observer and v = Hod for objects at cosmological distances 135 be aware of the controversy over the age and ultimate fate of the universe associated with the value of the Hubble Constant and the possible existence of dark matter 136 explain the concept of nuclear binding energy, and recognise and use the expression Δ E = c2Δm and use the non SI atomic mass unit (u) in calculations of nuclear mass (including mass deficit) and energy 137 describe the processes of nuclear fusion and fission 138 explain the mechanism of nuclear fusion and the need for high densities of matter and high temperatures to bring it about and maintain it |