Explanation of Equation 14.7

[loryruta]

I'm going through Chapter 14 (The Equation of Transfer).

I don't understand how, in Equation 14.7, the "Medium term" is simplified to only Ln.

Starting from:

My understanding is that we choose q to be equal to T_maj, so that the "Surface term" becomes only Lo.

The second term's estimator is this:

that if we properly sample t' according to p(t) = sigma_t * T_maj, it becomes just:

So my question is: isn't L_n missing the denominator 1 - q i.e. 1 - T_maj? Otherwise I don't understand how it gets simplified.

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P.S.: I'm not sure this is the ideal place to ask such questions...