Reciprocals

Two numbers that multiply to equal one.

When one goes up, the other goes down.

2 × ½ = 1 3 × ⅓ = 1 5 × ⅕ = 1
1/2 × 2 = 2/2 = 1
Number → ↑ Its Reciprocal 1 2 3 4 5 0 1 2

No matter where you drag, the product is always exactly one. That is what makes these numbers reciprocals.

Drag the dot along the curve

SPI Exam Topic

The Reciprocal Pair That Matters Most

Frequency and Period are reciprocals. Multiply them together and the answer is always one.

1 MHz × 1 µs
= 1
2 MHz × 0.5 µs
= 1
4 MHz × 0.25 µs
= 1
5 MHz × 0.2 µs
= 1
1 MHz: 1 cycle per microsecond
Period and Frequency are the most important reciprocal pair in ultrasound. They will come up constantly.

Quick Check

See if you can spot the reciprocals.

Question 01
Two reciprocals multiply to equal:
Concept Recall

Question 02
If a transducer's frequency doubles from 2 MHz to 4 MHz, the period:
Concept Recall

Question 03
Which pair are reciprocals?
Concept Recall

Review Complete!

You've finished the reciprocals check-in.