What happens to the wave when the wave's speed changes as it crosses a boundary between two different media?

When a wave crosses the boundary between two different media, its speed generally changes due to differences in physical properties such as density and elasticity. This change in speed causes a change in direction, which is known as refraction.

As the wave enters the second medium at an angle, the change in speed causes part of the wave to change its velocity and course. According to Snell's Law, the relationship between the angle of incidence and the angle of refraction depends on the ratio of the speeds of the wave in the two different media. This bending of the wave as it transitions from one medium to another is a fundamental aspect of wave behavior and plays a significant role in various applications, such as lens design, optical fibers, and sonar.

In contrast, reflection refers to the bouncing back of a wave when it hits a barrier, dissociation does not apply to physical wave behavior in this context, and the wavelength of the wave does actually change when the speed varies, as they are related through the equation (v = f\lambda), where (v) is speed, (f) is frequency, and (λ) is wavelength. Thus, the correct choice highlights the critical interaction of waves with different materials and their subsequent directional changes