Plane wave fronts are shown in two mediums. Find the refractive index of the second medium

Spacing between two consecutive wavefronts represents wavelength of a wave.Hence,  λ1 = 2m    and    λ2 = 1m   Also, refractive index , μ=cfλ  In refraction speed of light c and frequency f doesn't change. ∴  μ ∝ λ  ⇒μ2μ1 = λ1λ2 ⇒μ21=21 ⇒μ2 = 2