Doctors and engineers use 'ultrasound' to look inside bodies and check welds in metal pipes. Which property makes ultrasound especially useful for this?
AIt is inaudible, so does not disturb the patient
BIt travels faster than light
CIts very high frequency (above 20 kHz) means short wavelengths, allowing detailed imaging and easy detection of reflections
DIt cannot be reflected — so it passes straight through
Answer & Solution
Correct answer: C. Its very high frequency (above 20 kHz) means short wavelengths, allowing detailed imaging and easy detection of reflections
Ultrasound's high frequency means short wavelengths, which let it 'see' fine details and detect echoes from small structures inside the body (or small flaws in a weld). Patients are mostly unbothered because they cannot hear the high frequencies — but that's a side benefit, not the working principle.
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