Full moon!
when Earth is exactly between the Moon and Sun, Earth's shadow falls upon the surface of the Moon, dimming it and sometimes turning the surface red over the course of a few hours.
Answer:
406 nm
Explanation:
We are given;
Wavelength; λ = 775 nm
Refractive index of Calcium fluoride with wavelength of 775 nm as seen in the graph attached is approximately 1.4308.
n = 1.4308
Formula for the thickness of the film that would destruct the light is;
t = (m + 0.5)(λ/2n)
Where m is the order of the thickness.
The first smallest thickness is at m = 0 while the second smallest thickness is at m = 1.
Thus;
t = (1 + 0.5)(775/(2 × 1.4308))
t ≈ 406 nm