medium difficulty6 min

Applications of Ultrasound

Ultrasound applications use sound waves of frequency above 20,000 Hz for detection, imaging, cleaning, navigation, and measuring distances.

In one line: Ultrasound sends, reflects, and reveals.

Practice This Concept

Understand it

Ultrasound is useful because it can be sent in a narrow beam and can reflect from small objects or boundaries.
SONAR uses reflected ultrasound to find underwater objects or depth.
Medical ultrasound forms images of internal organs by detecting reflections from body tissues.
Bats use ultrasonic echoes to locate obstacles and prey.

Example

In SONAR, a ship sends an ultrasonic pulse downward and receives its echo from the seabed to calculate depth.

Rule to remember

SONAR distance rule: distance = speed × echo time / 2, because the wave travels to the object and returns.

See it worked out

Follow the example line by line, then use the same method on new questions.

Worked example

1A SONAR pulse returns after 4 s in water.
2If speed of sound in water is 1500 m/s, depth = 1500 × 4 / 2 = 3000 m.

Method you can reuse

1Identify the application.
2State that ultrasound is sent out.
3It reflects from a boundary or object.
4The receiver detects the echo.
5Use echo time or reflection pattern to find distance or form an image.

Sketch it in your answer

Draw a ship sending ultrasonic waves to the seabed or object, with reflected waves returning to the receiver. Label transmitter, receiver, seabed or object, and echo path.

Check yourself

Answer the question in your head before opening the answer.

Try it yourself

Why is ultrasound used in SONAR instead of ordinary audible sound?

Think first, then show answer

Ultrasound is used in SONAR because its high frequency and short wavelength help it travel as a directed beam and reflect clearly from underwater objects.

Common wrong answer

SONAR uses ultrasound because humans can hear it clearly underwater.

Why it loses marks: Ultrasound is above human hearing range.

Don't mix this up

Students often think ultrasound is chosen because it is louder. It is chosen mainly because of high frequency, short wavelength, and useful reflection.

Exam tip

For application answers, mention transmitted ultrasound, reflected echo, and calculation or image formation from the return signal.