2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/219755The nature of scalar wave functions near the horizon of Reissner Nordstrom (RN) extremal and Schwarzschild-de Sitter (SdS) extremal black holes are found using WKB approximation and the effect of reflection of waves from the horizon. The absorption cross section $σ_{abs}$ when RN extremal and SdS extremal black holes placed in a Klein-Gordon field is calculated.11 pages, Preprint to IJMPAGeneral Relativity and Quantum Cosmologytext