A thin film of oil with a thickness of 90 nm rests on top of a pool of water. When white light incident on the film is reflected, what color (wavelength of the first order) is seen? The refractive index of the oil is noil =1.45 and of water is nwater=1.33

m=0,  λ₀  = 522 10⁻⁹ m

Explanation:

In this case we can see that the first boy M The reflected light suffers an interference phenomenon, let's analyze what happens on each surface

* When light passes from a medium with a lower refractive index to a medium with a higher refractive index, it undergoes a phase change of pi rad (180º).

  This occurs when passing from air to oil, but not at the oil-water interface.

* within the material the wavelength changes by the refractive index

        λₙ = λ₀ / n

therefore introducing this into the constructive interference equation and assuming almost perpendicular incidence remains

         2 t = (m + ½) λₙ

         2t = (m + ½) λ₀ / n

        λ₀ = 2t n / (m + ½)

light in the first order (m = 1)

       λ₀  = 2 90 10⁻⁹ 1.45 / (1+ ½)

       λ₀  = 174 10⁻⁹ m

the light for zero order (m = 0)

         λ₀ = 2 90 10⁻⁹ 1.45 / (0+ ½)

         λ₀  = 522 10⁻⁹ m

this radiation in the visible range in the green region

the answer is f1 and d2 because if you put equal force on those two points the beam would balance trust me on this

force tends to be low and long diustance masses are high