I am a material engineer and have a question about a formula derivation regarding microwave absorption properties. I really cannot figure it out after days of trying. This should be simple for a specialist.

In this attached paper, how could one derive Eq(10) based on Eq (8) and (9)? Is k_2 in Eq (8) a complex number? Source: https://www.researchgate.net/profil...of-the-permeable-base-transistor.pdf#page=168

I am a material engineer and have a question about a formula derivation regarding microwave absorption properties. I really cannot figure it out after days of trying. This should be simple for a specialist.

In this attached paper, how could one derive Eq(10) based on Eq (8) and (9)? Is k_2 in Eq (8) a complex number? Source: https://www.researchgate.net/profile/Sture-Petersson/publication/230997780_Semi-analytic_model_of_the_permeable_base_transistor/links/02e7e530bd23818ff0000000/Semi-analytic-model-of-the-permeable-base-transistor.pdf#page=168