What is the wavelength of the light entering an interferometer if 402 bright fringes are counted when the movable mirror moves 0.115 mm?

The  value is  

Explanation:

From the question we are told that

    The  number of  bright fringes is  n =  402

     The  displacement of the mirror is  

Generally the number of fringes is mathematically represented as

=>    

=>    

=>  

answer; how far out of place which the object finished relative to the starting location;