Change in direction and velocity of a wave front due to its passing from one medium into another of differing density describes which propagation effect?

The change in direction and velocity of a wave front as it passes from one medium to another with differing density is known as refraction. This phenomenon occurs because waves travel at different speeds in different media due to variations in physical properties like density. When a wave enters a new medium at an angle, its speed changes, causing it to bend. Refraction is essential in various applications, including optics and telecommunications, where understanding how waves behave when transitioning between materials is crucial for designing effective systems.

Attenuation refers to the reduction in signal strength as it travels through a medium, while diffraction is the bending of waves around obstacles or openings. Reflection describes the bouncing back of waves when they hit a boundary between two different media. None of these options involve the change in wave direction and velocity due to differences in medium density, which is fundamental to the concept of refraction.