A thick glass slab with is viewed in reflected white light

PHYSICS · Subjective · AP · Physics 2: Algebra-based · Waves Sound and Physical Optics · Waves Sound and Physical Optics

Problem

A thick glass slab with

\mu=1.5

is viewed in reflected white light. It is proposed to coat the slab with a thin layer of refractive index

1.3

so that wavelength

6000\,\text{\AA}

is suppressed. Find the minimum thickness of the coating required.