What is defined by the term "conservation of energy" in the context of oblique incidence?

The term "conservation of energy" in the context of oblique incidence refers to the principle that the total intensity of energy entering a boundary must equal the total intensity of energy exiting that boundary, accounting for reflection and transmission. This means that when a wave, such as an ultrasound wave, encounters a boundary at an angle, the energy is not created or destroyed; rather, it is redistributed between reflected and transmitted components.

When a wave reflects off a surface, part of the wave's energy is reflected back, while the remainder is transmitted into the next medium. The combined intensity of both the reflected and transmitted waves will equal the intensity of the incident wave hitting the boundary. This reflects the fundamental law of conservation of energy, which states that energy cannot be created or destroyed in an isolated system.

The other options do not accurately align with this principle. While some energy may be absorbed or lost, the key concept of conservation of energy focuses on the balance between incident, reflected, and transmitted intensities rather than their specific pathways or losses in energy.