* Reflection: Some of the light is reflected back at the boundary between the two media. This is more pronounced if the difference in refractive indices between the two media is large.

* Absorption: The denser medium may absorb some of the light energy, converting it into other forms like heat. This is dependent on the specific material.

* Scattering: Light can be scattered in various directions within the denser medium, leading to a reduction in the intensity of the original beam.

However, there's a key factor to consider: the angle of incidence. If light enters the denser medium at a normal angle (perpendicular to the surface), the intensity *may* remain relatively unchanged. This is because reflection is minimized at normal incidence.

Overall, the intensity of light generally decreases when it enters a denser medium, but the exact change depends on factors like the angle of incidence, the materials involved, and the wavelength of light.