AERONET sun photometer as a didactic tool for understanding aerosol refractive index in the atmosphere: a case study for central Amazon - Franco, Marco A.; Tavares, Pedro H.T.; Rizzo, Luciana Varanda; Morais, Fernando G.; Palácios, Rafael; Artaxo Netto, Paulo Eduardo (Revista Brasileira de Ensino de Física, 2025)