ULTRASOUND PHYSICS SPI REVIEW
ACTUAL TEST PAPER 2026 QUESTIONS
WITH SOLUTIONS GRADED A+
⩥ Acoustic impedance is defined as the product? Answer: density (in
kg/m^3) and speed of sound (in m/s) in the tissue.
⩥ measurement for frequency. Answer: Hz
⩥ Transducer of 1.5MHz gives what wavelength? (in mm). Answer: 1
mm wavelength = 1.5 MHz transducer
⩥ ___ = distance between areas of compression. Answer: Wavelength
⩥ equation for speed. Answer: speed = wavelength x freq
⩥ US assumes everything travels at what speed. Answer: 1540 m/s
⩥ Speed is (fast/slow) in air? what about in bone?. Answer: Air: slow
Bone: fast
,⩥ when speed changes in various media (wavelength/frequency)
changes. ___ stays constant. Answer: - wavelength changes
- freq stays same
⩥ a change of 10 in dB scale corresponds to ___ orders of magnitude.
Answer: 2 orders of magnitude (100 times)
⩥ reducing the sound intensity to 10% is ___dB. Answer: -10
⩥ reducing the sound intensity to 1% is ___dB. Answer: -20
⩥ reducing the sound intensity to 0.1 % is ___dB. Answer: -30
⩥ a loss of ___ dB represents a 50% loss of signal intensity (power).
Answer: 3 (-3dB)
⩥ what is the half value thickness in US. Answer: the tissue thickness
that reduces the US intensity by 3dB
⩥ what are the 4 interactions of US with matter. Answer: reflection
refraction
scattering
absorption
,⩥ ____ is the interaction of US energy due to the differences in the
acoustic impedance of two tissues. Answer: reflection
⩥ the compressibility of a spring is similar to. Answer: impedance
⩥ what is equation for impedance. Answer: z = density x speed of sound
⩥ is reflection from similar tissues big or small?. Answer: Small
difference in "impedance" (similar tissues) results in a SMALL
reflection.
⩥ is reflection from two different tissues big or small. Answer: large
difference in "impedance" results in a LARGE reflection
⩥ what 2 things influence refraction. Answer: 1) speed change - based
on tissue compression
2) angle of incidence
⩥ ___ describes a change in direction of transmitted US energy at a
tissue boundary when the beam is not perpendicular to said boundary.
Answer: refraction
⩥ what factors influence refraction? (2). Answer: - speed change
, - angle of incidence
⩥ Snells law applies to what concept. Answer: refraction
⩥ what happens to the ultrasound beam is perpendicular to the surface?.
Answer: part of the beam bounces back and part of it goes right on
through
- because there is no incident angle, there is no refraction
⩥ what happens to refraction if the speed of sound is the same in two
media?. Answer: there is NO REFRACTION
- no refraction if incident angle is perpendicular as well
⩥ what is the "critical angle". Answer: this is the angle at which
complete reflection
- speed difference and angle of incidence is great enough
- essentially, the reflected waves will not get back to transducer
⩥ what is a clinical example of refraction?. Answer: as sound passes
from tissue to fluid, there is a change in speed
- creates a bending of the beam
- typically along the edges of fluid fill structures like the gallbladder
ACTUAL TEST PAPER 2026 QUESTIONS
WITH SOLUTIONS GRADED A+
⩥ Acoustic impedance is defined as the product? Answer: density (in
kg/m^3) and speed of sound (in m/s) in the tissue.
⩥ measurement for frequency. Answer: Hz
⩥ Transducer of 1.5MHz gives what wavelength? (in mm). Answer: 1
mm wavelength = 1.5 MHz transducer
⩥ ___ = distance between areas of compression. Answer: Wavelength
⩥ equation for speed. Answer: speed = wavelength x freq
⩥ US assumes everything travels at what speed. Answer: 1540 m/s
⩥ Speed is (fast/slow) in air? what about in bone?. Answer: Air: slow
Bone: fast
,⩥ when speed changes in various media (wavelength/frequency)
changes. ___ stays constant. Answer: - wavelength changes
- freq stays same
⩥ a change of 10 in dB scale corresponds to ___ orders of magnitude.
Answer: 2 orders of magnitude (100 times)
⩥ reducing the sound intensity to 10% is ___dB. Answer: -10
⩥ reducing the sound intensity to 1% is ___dB. Answer: -20
⩥ reducing the sound intensity to 0.1 % is ___dB. Answer: -30
⩥ a loss of ___ dB represents a 50% loss of signal intensity (power).
Answer: 3 (-3dB)
⩥ what is the half value thickness in US. Answer: the tissue thickness
that reduces the US intensity by 3dB
⩥ what are the 4 interactions of US with matter. Answer: reflection
refraction
scattering
absorption
,⩥ ____ is the interaction of US energy due to the differences in the
acoustic impedance of two tissues. Answer: reflection
⩥ the compressibility of a spring is similar to. Answer: impedance
⩥ what is equation for impedance. Answer: z = density x speed of sound
⩥ is reflection from similar tissues big or small?. Answer: Small
difference in "impedance" (similar tissues) results in a SMALL
reflection.
⩥ is reflection from two different tissues big or small. Answer: large
difference in "impedance" results in a LARGE reflection
⩥ what 2 things influence refraction. Answer: 1) speed change - based
on tissue compression
2) angle of incidence
⩥ ___ describes a change in direction of transmitted US energy at a
tissue boundary when the beam is not perpendicular to said boundary.
Answer: refraction
⩥ what factors influence refraction? (2). Answer: - speed change
, - angle of incidence
⩥ Snells law applies to what concept. Answer: refraction
⩥ what happens to the ultrasound beam is perpendicular to the surface?.
Answer: part of the beam bounces back and part of it goes right on
through
- because there is no incident angle, there is no refraction
⩥ what happens to refraction if the speed of sound is the same in two
media?. Answer: there is NO REFRACTION
- no refraction if incident angle is perpendicular as well
⩥ what is the "critical angle". Answer: this is the angle at which
complete reflection
- speed difference and angle of incidence is great enough
- essentially, the reflected waves will not get back to transducer
⩥ what is a clinical example of refraction?. Answer: as sound passes
from tissue to fluid, there is a change in speed
- creates a bending of the beam
- typically along the edges of fluid fill structures like the gallbladder
