Which statement best describes how frequency affects the depth of heating?

Which statement best describes how frequency affects the depth of heating?

• A. Higher frequency penetrates deeper
• B. Lower frequency penetrates deeper
• C. Frequency has no effect on depth
• D. Depth depends only on tissue type

Answer: (B)

Lower frequency energy penetrates deeper into tissue because attenuation and absorption increase with frequency. In therapeutic ultrasound, energy at a lower frequency (for example, around 1 MHz) travels farther before being absorbed, so it heats deeper structures. Higher frequency energy is absorbed more readily in superficial layers, leading to heating that’s more shallow. So, as frequency decreases, depth of heating increases, though the exact depth also depends on tissue properties and how the ultrasound is applied (continuous vs pulsed, intensity, etc.). The general takeaway is that lower frequency yields deeper heating, whereas higher frequency confines heating to superficial tissues.

Lower frequency energy penetrates deeper into tissue because attenuation and absorption increase with frequency. In therapeutic ultrasound, energy at a lower frequency (for example, around 1 MHz) travels farther before being absorbed, so it heats deeper structures. Higher frequency energy is absorbed more readily in superficial layers, leading to heating that’s more shallow. So, as frequency decreases, depth of heating increases, though the exact depth also depends on tissue properties and how the ultrasound is applied (continuous vs pulsed, intensity, etc.). The general takeaway is that lower frequency yields deeper heating, whereas higher frequency confines heating to superficial tissues.