Penetration depth scattering media

The resolution of the ultrasonic microscope is determined by the aperture and sound wavelength. The sound wavelength, in turn, is determined by the ultrasonic frequency. Using water as the coupling medium, the maximiun resolution is 0.4 pm at 2 GHz, 15 pm at 100 MHz, and 500 pm at 10 MHz. The penetration depth depends on the frequency, the type of material, and the surface quality of the specimen. The scattering of the sound on the specimen surface is influenced by its roughness. The penetration depth can reach several millimeters at low sound frequencies. 

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