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.
Related questions
Why does a damaged eardrum lead to hearing impairment?Which of the following is NOT an effective way of reducing noise pollution in a city neighVocal cord length is about 20 mm in men, 15 mm in women, and much shorter in young childreSound from a small bell is heard inside a swimming pool when the bell is rung underwater. Two bells A and B are struck. A has the SAME loudness as B but a HIGHER pitch. Which stateIf the amplitude of a vibration doubles, the loudness of the sound produced:Sound travels through a solid (like a wooden ruler) MORE easily than through air mainly beBats and dogs can hear sounds well beyond what humans can. Police use a special whistle th