scholarly journals Diffraction of Light by High-Frequency Ultrasonic Waves

Nature ◽  
1947 ◽  
Vol 159 (4034) ◽  
pp. 267-267 ◽  
Author(s):  
S. BHAGAVANTAM ◽  
B. RAMACHANDRA RAO
Keyword(s):  
High Frequency ◽  
Ultrasonic Waves ◽  
Diffraction Of Light

scholarly journals Diffraction of Light by Very High Frequency Ultrasonic Waves

Nature ◽  
1948 ◽  
Vol 161 (4102) ◽  
pp. 927-927 ◽  
Author(s):  
S. BHAGAVANTAM ◽  
B. RAMACHANDRA RAO
Keyword(s):  
High Frequency ◽  
Ultrasonic Waves ◽  
Very High Frequency ◽  
Diffraction Of Light ◽  
Very High

INTENSITY MEASUREMENTS IN THE DIFFRACTION OF LIGHT BY ULTRASONIC WAVES

1936 ◽  
Vol 14a (8) ◽  
pp. 158-171 ◽  
Author(s):  
F. H. Sanders
Keyword(s):  
High Frequency ◽  
Light Wave ◽  
Monochromatic Light ◽  
Sound Intensity ◽  
Ultrasonic Waves ◽  
Torsion Pendulum ◽  
Intensity Measurements ◽  
Diffraction Of Light ◽  
Absolute Measurements ◽  
Good Agreement

Measurements of the distribution of light energy among the various orders of the diffraction pattern produced when monochromatic light is passed through a liquid subjected to high-frequency ultrasonic disturbances have been carried out over a range of ultrasonic intensities at frequencies in the region of 5 megacycles per second. Both progressive and standing wave fields have been studied. Results of the experiments show excellent agreement with the theory of Raman and Nath for the variation in degree of scattering with varying ultrasonic intensity. Absolute measurements of the sound intensity conducted with a torsion pendulum are in good agreement with that expected from the theory for the liquids and light wave-lengths involved.

scholarly journals High Frequency Ultrasonic Wave Propagation in  Anisotropic Materials

2021 ◽  
Author(s):  
◽  
Andrew Paul Dawson
Keyword(s):  
Wave Propagation ◽  
Ultrasonic Wave ◽  
High Frequency ◽  
Guided Wave ◽  
Ultrasonic Waves ◽  
Tissue Characterisation ◽  
Ultrasonic Wave Propagation ◽  
Matching Layer ◽  
Fibrous Tissues ◽  
Wave Modes

<p>The influence of highly regular, anisotropic, microstructured materials on high frequency ultrasonic wave propagation was investigated in this work. Microstructure, often only treated as a source of scattering, significantly influences high frequency ultrasonic waves, resulting in unexpected guided wave modes. Tissues, such as skin or muscle, are treated as homogeneous by current medical ultrasound systems, but actually consist of highly anisotropic micron-sized fibres. As these systems increase towards 100 MHz, these fibres will significantly influence propagating waves leading to guided wave modes. The effect of these modes on image quality must be considered. However, before studies can be undertaken on fibrous tissues, wave propagation in more ideal structures must be first understood. After the construction of a suitable high frequency ultrasound experimental system, finite element modelling and experimental characterisation of high frequency (20-200 MHz) ultrasonic waves in ideal, collinear, nanostructured alumina was carried out. These results revealed interesting waveguiding phenomena, and also identified the potential and significant advantages of using a microstructured material as an alternative acoustic matching layer in ultrasonic transducer design. Tailorable acoustic impedances were achieved from 4-17 MRayl, covering the impedance range of 7-12 MRayl most commonly required by transducer matching layers. Attenuation coefficients as low as 3.5 dBmm-1 were measured at 100 MHz, which is excellent when compared with 500 dBmm-1 that was measured for a state of the art loaded epoxy matching layer at the same frequency. Reception of ultrasound without the restriction of critical angles was also achieved, and no dispersion was observed in these structures (unlike current matching layers) until at least 200 MHz. In addition, to make a significant step forward towards high frequency tissue characterisation, novel microstructured poly(vinyl alcohol) tissue-mimicking phantoms were also developed. These phantoms possessed acoustic and microstructural properties representative of fibrous tissues, much more realistic than currently used homogeneous phantoms. The attenuation coefficient measured along the direction of PVA alignment in an example phantom was 8 dBmm-1 at 30 MHz, in excellent agreement with healthy human myocardium. This method will allow the fabrication of more realistic and repeatable phantoms for future high frequency tissue characterisation studies.</p>

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