Eighth Grade · Science · week 19

Wave properties and math

Define wavelength, frequency, amplitude, and period, and apply wave speed = frequency x wavelength.

Waves carry energy through repeating motion. Wavelength is the distance from one point on a wave to the same point on the next repeat (crest to crest), measured in meters. Frequency is how many complete waves pass a point each second, measured in hertz (Hz) -- 1 Hz means one wave per second.

Amplitude is the height of the wave from its resting position, which relates to how much energy it carries. Period is the time for one complete wave, the flip side of frequency: period = 1 / frequency. All of these connect through one equation: wave speed = frequency x wavelength.

📋 For the teacher
Teach it (10–15 min):
  • Draw a simple wave together and label wavelength (crest to crest) and amplitude (height from the resting line) on the picture.
  • Practice the wave speed equation in all three directions: solving for speed, frequency, and wavelength.
  • Connect period and frequency as reciprocals: a wave with a 2-second period happens 0.5 times per second.
Talk about it:
  • What is the difference between wavelength and amplitude?
  • Why do frequency and wavelength have an inverse relationship when speed stays the same?

Mastery looks like: They apply wave speed = frequency x wavelength to solve for any one quantity, and identify wavelength and amplitude on a described wave.

Common stumbles: Confusing wavelength (a distance) with period (a time); forgetting that frequency and period are reciprocals.

Homework for this lessonType it, write it with a stylus, or print it for pencil & paper.open →
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