An Oil Film with Refractive Index 1

Multiple Choice

An oil film with refractive index 1.48 and thickness 290 nm is floating on water and illuminated with white light at normal incidence.What is the wavelength of the dominant color in the reflected light?

A) green (541 nm)
B) blue-green (493 nm)
C) violet (404 nm)
D) yellow (572 nm)
E) blue (470 nm)