Transverse Waves

Contributor: Meghan Vestal. Lesson ID: 11500

What can a rubber duck teach you about light? How long would it take you to travel to the sun? Watch a simple video, work on a worksheet, get out a piece of rope, and learn about crests and troughs!



learning style
Kinesthetic, Visual
personality style
Grade Level
Middle School (6-8)
Lesson Type
Dig Deeper

Lesson Plan - Get It!

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  • How fast does light move?

When you sit in the sun to "catch a few rays," you're probably not being literal!

  • Do you think light travels fast or slow?

Tell your teacher or parent.

Light could easily beat the fastest car in a NASCAR race, and can travel from New York to London faster than any jet!

Light travels at a speed of 186,000 miles per second! It takes light less than eight and a half minutes to travel 93 million miles, from the sun to earth. Now that's fast!

Light travels as a transverse wave. To learn exactly what a transverse wave is, watch the video Physics - Waves – Introduction. by expertmathstutor (below):

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What is the difference between a transverse wave and a longitudinal wave?

  • In a transverse wave, the vibrations are perpendicular to the direction the wave is traveling.
  • In a longitudinal wave, the vibrations are parallel to the direction the wave is traveling.

Get a Slinky, if you have one. Hold one end of the Slinky while your teacher or parent holds the other end a few feet away from you. Hold your end still while your teacher or parent moves their end up and down. You have just created a transverse wave. Discuss what you observed about the movement of the Slinky with your teacher or parent.

There are four terms you need to know when studying a transverse wave: crest, trough, wavelength, and frequency. These terms were also discussed in the video.

A crest is the highest point on a wave, and a trough is the lowest point on a wave.

wave diagram

Wavelength describes the distance between two waves. A wavelength can be measured from any point on a wave, as long as it is measured to the same point on the next wave. Point to where the wavelength is labeled below:

wavelength diagram

When measuring wavelengths, use the metric units millimeters and centimeters unless another unit is specified. You have to know what a wavelength is in order to find the frequency.

Frequency is the number of wavelengths (or cycles) in a wave during a fixed period of time, usually seconds.

Look at the picture below, illustrating one second.

  • What is the frequency of the wave?

one second

  • Did you say two?

That's correct! The light wave pictured has a frequency of two cycles per second because there are two full wavelengths pictured.

The frequency of a light wave is proportional to its energy. A high-frequency wave has high energy. A low-frequency wave has low energy.

  • Do the waves pictured above have high or low energy?

Share your answer with a teacher or parent and explain your reasoning.

Think you understand all the parts of a light wave? Move on to the next section to find out!

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