1. Department of Physics , Government General Degree College at Kushmandi , Dakshin Dinajpur , India
2. Department of Physics , Jadavpur University , Kolkata , 700032 , India
3. Institute of Natural Sciences and Applied Technology , Kolkata , 700032 , India
4. Department of Mathematics , Government General Degree College at Kushmandi , Dakshin Dinajpur , 733121 , India