Two plano-convex thin glass lenses are brought into contact with their spherical surfaces. Find the optical power of such a system if in reflected light with wavelength λ=0.60μm\lambda=0.60 \mu \mathrm{m}λ=0.60μm the diameter of the fifth bright ring is d=1.50 mmd=1.50 \mathrm{~mm}d=1.50 mm.