When light is refracted into a medium;

Wavelength and frequency increasess Wavelength increases frequency decreases Wavelength changes, the frequency remains the same Nothing changes

Wavelength changes, the frequency remains the same

When light is refracted into a medium its speed changes but the frequency remains the same because the energy associated with a photon of this light is proportional to the frequency of the light and it remains unchanged. Since the wavelength λ = c/, i.e. λ ∝ c. So the wavelength changes.