The solution of the problem 3.25 cr 3 from the problem

The solution of the problem 3.25 cr 3 from the problem

Task 3.25
To eliminate the reflection of light on the surface of the glass lens, a film of the substance with
The index of refraction is 1.3 smaller than that of glass. At what is the smallest thickness of this film
Reflection of light with a wavelength of 0.48 μm will not be observed if the angle of incidence of the rays is 30 °?