SPEKTRA Volume 3 issue 2 contains 7 papers: 1) Fabrication and Characterization of The Composites of Resin - Husk of Rice and Resin - Rub Ash, 2) UV-Visible Optical Absorbance of Graphene Oxide in Copper Ionic Liquid Synthesized via Electrochemical Method Assisted by a Copper Coil, 3) Flow Units Determination Using Flow Zone Indicator for Carbonate Reservoir, 4) Optical Properties Analyses of Chlorophyll of Leaf Extract by UV-VIS Spectrometer as Pre-Study of Dye Sensitizer, 5) Imaging of 3-D Seismic Tomography for Internal Structure Under The Mountain Merapi Using The Lotos-10 Software, 6) Analog Computer for Studying Diatomic Molecular Spectra in Terahertz Frequency, 7) Two Static Fluid Dark Matter Model with Additional Cosmological Constant.