If an angle of incidence is not measured at 90 degrees, it is referred to as what?

When an angle of incidence is not measured at 90 degrees, it is typically referred to as oblique. The term "oblique" signifies that the angle deviates from the standard perpendicular incidence, which is at 90 degrees. In the context of sonography and wave interactions, an oblique angle can significantly affect how waves are transmitted or reflected, influencing the quality and accuracy of imaging.

Understanding the nature of oblique incidence is crucial as it pertains to scenarios such as sound propagation in tissues, impedance matching, and the resultant reflection or transmission coefficients. This contrasts with angles described as acute (less than 90 degrees) or obtuse (greater than 90 degrees), which do not universally apply to non-perpendicular incidences. Other terms like "reflected" refer specifically to the behavior of waves upon striking a surface, rather than the angle of incidence. Recognizing and utilizing the term "oblique" is essential for interpreting and analyzing ultrasound interactions accurately.