Department of Physics and Astrophysics, University of Delhi, Delhi 110007, India. areejit@physics.du.ac.in|Department of Physics and Astrophysics, University of Delhi, Delhi 110007, India. areejit@physics.du.ac.in|Department of Physics and Astrophysics, University of Delhi, Delhi 110007, India. areejit@physics.du.ac.in|Department of Physics and Astrophysics, University of Delhi, Delhi 110007, India. areejit@physics.du.ac.in|Department of Physics and Astrophysics, University of Delhi, Delhi 110007, India. areejit@physics.du.ac.in|Department of Physics and Astrophysics, University of Delhi, Delhi 110007, India. areejit@physics.du.ac.in