What happens to the half layer thickness as frequency increases?

As frequency increases, the half layer thickness decreases. This relationship is primarily due to the fact that higher frequency ultrasound waves have shorter wavelengths and are more readily absorbed by tissue. The half layer thickness is a measure of the depth of tissue required to attenuate the intensity of the ultrasound beam to half its original value. Since higher frequencies are subject to greater attenuation due to their increased absorption, the distance required to reach that half intensity point is reduced, resulting in a thinner half layer thickness at higher frequencies. This principle is important in sonography as it affects image quality and the choice of frequency for different clinical applications.