1. Department of Physics, Faculty of Science, University of Bamenda, P.O. Box 39, Bambili, Cameroon
2. Department of Physics, Faculty of Science, University of Maroua, P.O. Box 814, Maroua, Cameroon
3. Department of Physics, Higher Teachers Training College, University of Maroua, P.O. Box 46, Maroua, Cameroon