1. a Physics Section, School of Distance Education, Universiti Sains Malaysia, 11800 Penang, Malaysia; ; chuahleesiang@usm.my, Email: chuahleesiang@yahoo.com
2. b School of Physics, Universiti Sains Malaysia, 11800 Minden, Penang, Malaysia
3. c School of Physics, Universiti Sains Malaysia, 11800 Minden, Penang, Malaysia
4. d School of Physics, Universiti Sains Malaysia, 11800 Minden, Penang, Malaysia
5. e School of Physics, Universiti Sains Malaysia, 11800 Minden, Penang, Malaysia