(a) How many fringes appear between the first diffraction-envelope minima to either side of the central maximum in a double-slit pattern if λ = 471 nm, d = 0.117 mm, and a = 35.7 µm? (b) What is the ratio of the intensity of the third bright fringe to the intensity of the central fringe?

a

The number of fringe is  z  = 3 fringes

b

The  ratio is

Explanation:

a

 From the question we are told that

        The wavelength is  

        The distance between the slit is  

        The width of the slit is  

let  z be the number of fringes that appear between the first diffraction-envelope minima to either side of the central maximum in a double-slit pattern is  and this mathematically represented as

Substituting values

             z  = 3 fringes

b

   From the question  we are told that the order  of the bright fringe is  n = 3

   Generally the intensity of  a pattern  is mathematically represented as

Where is the intensity  of the  central fringe

 And  Generally  

if the person is shown to have +90n, then ans is -10n.

if the person is shown to have -90n, then ans is +10n.