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Rybicki & Lightman, Revised Edition Chapter 1. Fundamentals of Radiative Transfer Problem 07. The Einstein coefficients Solution Acknowledgment Thank you, Mateus, for asking this question.
Rybicki & Lightman, Revised Edition Chapter 1. Fundamentals of Radiative Transfer Problem 01. Definition of the flux and solid angle Solution
In this page, I will post solutions of the problems in the Radiative Processes in Astrophysics (Revised Edition), written by Rybicki & Lightman. You can buy the book via https://www.amazon.com/Radiative-Processes-Astrophysics-George-Rybicki/dp/0471827592