Answer:
The minimum thickness of the film and the wavelength of the light in air are
and 371 nm.
Explanation:
Given that,
Refractive index of soap= 1.34
Refractive index of glass= 1.55
Wavelength = 642 nm
(I). We need to calculate the minimum thickness
Using formula of thickness

Where, m = 0 for constrictive
Put the value into the formula


(II). We need to calculate the wavelength
Using formula of wavelength

Where, m = 1
Put the value into the formula


Hence, The minimum thickness of the film and the wavelength of the light in air are
and 371 nm.