ARDMS Ultrasound Physics & Instrumentation Practice Exam

How can spatial pulse length be calculated?

1. Dividing wavelength by frequency

2. Multiplying the number of cycles times the wavelength

3. Adding wavelength to frequency

4. Subtracting cycles from wavelength

The correct answer is: Multiplying the number of cycles times the wavelength

Spatial pulse length is the physical length of one pulse of sound and is determined by the number of cycles in that pulse and the wavelength of those cycles. To calculate spatial pulse length, you multiply the number of cycles in the pulse by the wavelength of the sound wave. This relationship makes sense because the spatial pulse length reflects the total distance that the pulse occupies in space, which is a product of how many cycles are in the pulse and the size of each cycle (wavelength). If you think of a pulse as consisting of several complete cycles, each contributing a portion of the total length, multiplying the number of cycles by the wavelength effectively gives you a measure of the entire length of that pulse. In contrast, other calculations, such as dividing wavelength by frequency or adding wavelength to frequency, do not provide meaningful measurements of spatial pulse length and instead pertain to other aspects of wave behavior, such as calculating wave speed or sonic frequencies.