Pupil sheet · Echoes and ultrasound

Echoes and ultrasound — return questions

Name ______________________ Date ____________

Use one to two weeks after the lessons. Keep the notes and the lesson closed.

1. calculate

A swimmer at one end of an indoor pool shouts and hears the echo from the far wall 0.30 s later. The speed of sound in the air of the pool hall is 340 m/s. Calculate the length of the pool.

Length of the pool: ______________ unit ________

2. describe

Describe a method for determining the speed of sound in air using a large wall, a trundle wheel and a stop-clock. Include what is measured, how the timing is made reliable and how the speed is calculated.

What is measured

Making the timing reliable

Calculating the speed

3. define / explain

Define ultrasound. Then explain whether an 18 000 Hz tone from a phone app is ultrasound.

Definition

The 18 000 Hz tone

4. calculate

Supplement. During a scan, an echo from the back of an unborn baby’s head returns 65 µs after the pulse. Ultrasound travels through soft tissue at 1540 m/s (1 µs = 0.000 001 s). Calculate how far below the probe the back of the head is, in millimetres. Give your answer to 2 significant figures.

Depth below the probe: ______________ unit ________

5. identify

Supplement. A hospital scans a patient’s liver with ultrasound, and an engineer tests a steel rail for hidden cracks with ultrasound. Which row describes both correctly?

Row	In the body scan, the echoes come from	In the steel test, a crack inside shows as
A	boundaries between different tissues	an extra echo after the back-wall echo
B	boundaries between different tissues	an extra echo before the back-wall echo
C	the gel on the skin	an extra echo before the back-wall echo
D	sound made by the tissues themselves	an extra echo after the back-wall echo

Circle one answer.