Ultrasound Imaging via Echoes

Steps:

• Ultrasound scanner emits high-frequency sound waves into the body.
• Waves travel through tissues and encounter boundaries between different densities.
• At boundaries, some waves reflect back as echoes toward the scanner.
• Scanner detects echoes and uses timing/intensity to construct the image.

Why C is correct:

• Ultrasound imaging forms images from reflected echoes, per the principle of acoustic impedance mismatch causing partial reflection of sound waves.

Why the others are wrong:

• A: Absorbed ultrasound dissipates energy as heat, not forming detectable signals for imaging.
• B: Babies do not emit ultrasound; the scanner provides the initial waves.
• D: Refraction bends waves but does not produce the returning signals needed for image formation.

Final answer: C