question_answer

A thin sheet of mica (\[\mu \] m thick) is placed in the path of one of the interfering beams in a biprism arrangement. It is found that the central bright band shifts a distance equal to the width of a bright fringe. The refractive index of mica \[(Given\,\,\lambda =6\times {{10}^{-7}}\,m)\] is

A) 1.0  

B) 1.5   

C) 1.75

D) 1.25