r2 4- red 3 · a) From equations and 2, express ther dation pressure in terms of
ID: 3280414 • Letter: R
Question
r2 4- red 3 · a) From equations and 2, express ther dation pressure in terms of the luminosity, b) The effective cross section for electrons interacting with radiation is the Thomp- son scattering cross section,= 6.65 × 10-29 m2. For an electron in the outer atmosphere (i.e. above the burning zone) of a bursting neutron star with mass M, radius R, and luminosity L = L(t), what is the average force due to radiation neutron radius R,andluminositburningtonehatis pressure? c) In what direction would you expect the sum of all forces on the electron to act? [3 + 2 + 3 = 8 marks]Explanation / Answer
3.
a. given
Prad = aT^4/3
L = 4*pi*R^2*sigma*T^4
hence
Prad = aT^4/3 = a*L/3*4*pi*R^2*sigma = aL/12pR^2*sigma
b. effective cross section of electron, sigmat = 6.65*10^-29 m^2
mass of star = M
radius = R
luminosity L(t)
so, radiation pressure, Prad = aL/12pR^2*sigma
Average force = Prad*sigmat = sigmat*aL/12pR^2*sigma
c. aqs this force is due to radiation pressure, sum of all these forces should act along the direction of the line joining the center of the star and the electron, pointing away from the star
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