ARDMS Ultrasound Physics & Instrumentation Practice Exam

In ultrasound physics, which of the following statements about the relationship between pressure and intensity is true?

1. High pressure always means high intensity

2. Pressure is independent of intensity

3. Intensity is proportional to the square of the pressure

4. Low pressure results in high intensity

The correct answer is: Intensity is proportional to the square of the pressure

The statement that intensity is proportional to the square of the pressure is grounded in the physics of ultrasound wave propagation. In acoustics, intensity (which is a measure of the power per unit area) can be mathematically defined in relation to pressure. The relationship is often expressed through the equation: \[ I = \frac{P^2}{Z} \] where \( I \) represents intensity, \( P \) is the pressure amplitude of the wave, and \( Z \) is the acoustic impedance of the medium through which the wave travels. This relationship demonstrates that if pressure increases, intensity increases with the square of that pressure. Therefore, a change in pressure leads to a quadratic change in intensity, making this statement accurate. Understanding this relationship is fundamental when analyzing wave behavior in ultrasound and helps in applications such as optimizing imaging techniques and interpreting Doppler results. The other statements do not accurately describe the relationship between pressure and intensity. For example, high pressure does not always mean high intensity, as other factors like impedance affect the outcome. Similarly, characterizing pressure as independent of intensity overlooks their inherently linked relationship established by the fundamental equations of wave physics. Lastly, the idea that low pressure results in high intensity contradicts the established proportional relationship, as lower