SME
Grade 4 Science · Physical Science
Waves: amplitude and wavelength
Use this for “4 waves fit along a 200 cm rope. What is the wavelength?”
Diagram
Crest to crest is one wavelength, 50 cm.
Rope length: 200 cm
This is an example. Type your own values to start a new problem.
Waves along the rope
×
Wavelength (cm)
=
Rope length (cm)
Formulas
4 × 50 = 200
Waves along the rope × wavelength = rope length
Assumptions
•
A wave is a repeating pattern: crest, trough, crest.
•
Wavelength is the distance from one crest to the next.
•
Shake the rope faster: more waves fit along it, and each one is shorter.
•
A cork on a wave bobs up and down. The wave moves on; the cork stays.
Step-by-step
WE KNOW
Rope length: 200 cm
Waves along the rope: 4
FIND
wavelength
Step 1 · Find wavelength
4 × ? = 200
Waves along the rope × wavelength = rope length
Divide the rope length by the waves: the length of one wave.
Wavelength = 200 ÷ 4
Wavelength = 50 cm
Check
Put the numbers back in. Both sides should match.
4 × 50 = 200 ✓
Topic check
See what you know: 5 questions on this topic
New questions each time. Pass to mark it complete.