ARDMS Ultrasound Physics & Instrumentation Practice Exam

Which law describes the amount of refraction that occurs at an interface?

1. Archimedes' Principle

2. Snell's Law

3. Newton's Law

4. Pascal's Principle

The correct answer is: Snell's Law

The law that describes the amount of refraction that occurs at an interface is Snell's Law. This law quantifies how light rays change direction when they pass from one medium into another with a different density, such as from air into water or from one type of tissue into another in medical ultrasound. Snell's Law is mathematically defined by the relationship between the angles of incidence and refraction and the velocities of sound or light in each medium. It states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant and is determined by the indices of refraction of the two media. This principle is essential in ultrasound physics, as understanding how sound waves refract at tissue interfaces influences image quality and diagnostic accuracy. In contrast, Archimedes' Principle, Newton's Law, and Pascal's Principle relate to different physical phenomena, such as buoyancy, motion, and fluid pressure, respectively, and do not address refraction of waves at an interface. Thus, Snell's Law is the key concept that accurately describes the behavior of waves as they encounter differing media.