Dear Afshan,

welcome,

please read the equation you displayed in the reference given in the link: https://books.google.com.eg/books?id=RVBfQCU933MC&pg=PA211&lpg=PA211&dq=w/pi(Int(ln(R(w))-ln(R(w%27))+/+w%5E2-w%27%5E2))dw)&source=bl&ots=t6IaiYTP3R&sig=LZegjHJ-fX3r43rXVRGcsR4-t04&hl=en&sa=X&ved=0ahUKEwjpmc_vn5TYAhVLC-wKHZO7DnsQ6AEILzAB#v=onepage&q&f=false

then you can calculate the phase angle of the reflection coefficient at any frequency w, phi(w) by integrating the reflectance R(w dash) over all possible frequencies as given in the formula.

If you can not perform the the integration please tell us.

The right formula is given in the freelance such that R(w) is the same as R(w dash) with w dash is substituted for w.

Best wishes

I know the formula, the main problem is that reflectance R(w dash) is a vector of reflectance numbers on every wavelength numbers(R1,w1; R2,w2; R3,w3; .....,Rn,wn), In a certain w, and variable (w dash) in the integral, formula the function of R(w dash) is unknown for me to put it in the formula and make integral from it.

In my interpretation correct?

Dear Afshan,

please compare the formula in your question and that in the reference . They are different. In the reference in the integral R(w) is substituted by R(w dash) such that one can one can get phi(w) at a given w while integrating over R(w).

Best wishes