Ultrasonic waves, like all other waves, exhibit diffraction.Recall that the minimum half angle of a beam is given by:
alpha = (1.22*lamda_m)/d
The wavelengths used in ultrasound imaging techniques are generallyin the range from 0.3 mm to 0.75 mm [longer waves (lowerfrequencies) penetrate more deeply but provide less resolution ofdetail than the short waves]. In order for an ultrasonic beam tospread by less than a centimeter after it has traveled across ahuman torso (20 cm), the source of the waves must be about 10 or 20times larger than the wavelength. The source of the waves is calleda transducer.
Question:
A transducer is 18.5 mm in diameter and emits a wave of wavelength0.50 mm. The beam travels a total distance of 37 cm through thepatient and back to the transducer. How much has the beam spreadafter returning to the transducer? (Hint: Start with the formula,alpha = (1.22*lamda_m)/d , and recall that this is the minimum HALFangle of the beam.)
__________________ mm
Ultrasonic waves, like all other waves, exhibit diffraction.Recall that the minimum half angle of a beam is given by:
alpha = (1.22*lamda_m)/d
The wavelengths used in ultrasound imaging techniques are generallyin the range from 0.3 mm to 0.75 mm [longer waves (lowerfrequencies) penetrate more deeply but provide less resolution ofdetail than the short waves]. In order for an ultrasonic beam tospread by less than a centimeter after it has traveled across ahuman torso (20 cm), the source of the waves must be about 10 or 20times larger than the wavelength. The source of the waves is calleda transducer.
Question:
A transducer is 18.5 mm in diameter and emits a wave of wavelength0.50 mm. The beam travels a total distance of 37 cm through thepatient and back to the transducer. How much has the beam spreadafter returning to the transducer? (Hint: Start with the formula,alpha = (1.22*lamda_m)/d , and recall that this is the minimum HALFangle of the beam.)
__________________ mm
