# Homework Help: Fraction of incident flux that escapes from a star

1. Nov 25, 2013

### ppy

If the flux entering such an atmosphere from the core of the star at a radius is r0 is F0,
the flux that reaches radius r is given by

F(r)=F0*e^k(r^-2-r0^-2)

where k is a constant

a) Write down a formula for the fraction of the incident flux that escapes from the star
entirely. {3}
b) If 50% of the flux escapes from a star where the base of this stellar atmosphere lies at a
radius r0, what percentage of the flux escapes if this atmosphere only starts at twice as
large a radius? {3}

Is the answer to (a) just F=F0*e^k(R^-2-r0^-2) where R=radius of star and then to find the fraction you just do F(R)/F(r)?

Thanks :)