Question

Consider a thin film with n=1.42, immersed in air, and a light of 650nm wavelength. Determine the thickness of film that will create reflected light that constructively interferes.

Answer 1

`343.31* 10^(-9)m`

Step-by-step explanation:

For constructive interference, condition is that ( m=0,1,2.....)

`2nt=(m+(1)/(2))\lambda`

Take for m=1,

`2nt=((3)/(2))\lambda`

Given that, the refractive index of a thin film is,

`n=1.42`

And the wavelength of the light is,

`\lambda=650 nm=650* 10^(-9)m`

Now,

`2t=(3)/(2)( (650* 10^(-9)))/(1.42) \\t=(3)/(4)( (650* 10^(-9)))/(1.42)\\t=343.31* 10^(-9)m`

Therefore, the thickness of film which create reflected light is
`343.31* 10^(-9)m`