Answer:
Refractive index = 1.15
Explanation:
As we know for constructive interference of reflected light the path difference of two reflected light rays must be integral multiple of the wavelength
so here we have
[tex]2\mu t = N\lambda[/tex]
now here we know that
[tex]\lambda = 626 nm[/tex]
[tex]thickness(t) = 271 nm[/tex]
now we have
[tex]2(\mu )(271 nm) = (626 nm)[/tex]
[tex]\mu = \frac{626}{542}[/tex]
[tex]\mu = 1.15[/tex]