As the medium becomes denser, the angle of refraction generally decreases. This is known as the Snell's law, which states that the angle of refraction is inversely proportional to the refractive indices of the two media. When light travels from a less dense medium (lower refractive index) to a denser medium (higher refractive index), it bends towards the normal (the line perpendicular to the surface separating the two media) and decreases its angle of refraction.
