What is the wavelength (in millimeters) of a 5 MHz ultrasound wave?

What is the wavelength (in millimeters) of a 5 MHz ultrasound wave?

• A. 0.308 mm
• B. 0.31 mm
• C. 3.08 mm
• D. 1.54 mm

Answer: (A)

Wavelength is the distance the wave travels in one cycle, so it equals the speed of sound divided by the frequency. In soft tissue, the speed of sound is about 1540 m/s. For a 5 MHz wave (5,000,000 Hz), the wavelength is 1540 / 5,000,000 = 0.000308 m, which is 0.308 mm when converted to millimeters. That is the precise value; rounding to two decimals gives about 0.31 mm. The other options correspond to different frequencies: 3.08 mm would come from around 0.5 MHz, and 1.54 mm from about 1 MHz.

Wavelength is the distance the wave travels in one cycle, so it equals the speed of sound divided by the frequency. In soft tissue, the speed of sound is about 1540 m/s. For a 5 MHz wave (5,000,000 Hz), the wavelength is 1540 / 5,000,000 = 0.000308 m, which is 0.308 mm when converted to millimeters. That is the precise value; rounding to two decimals gives about 0.31 mm. The other options correspond to different frequencies: 3.08 mm would come from around 0.5 MHz, and 1.54 mm from about 1 MHz.