Wavelength facts for kids

A wavelength is the distance over which a wave's shape repeats. Imagine a wave like a wavy line; the wavelength is the length of one complete "wiggle" or cycle of that wave. All waves, from sound to light, can be thought of as being made up of simpler waves called sine waves.

A sine wave, showing its wavelength

Water waves repeating, with the wavelength marked as λ

What are waves?

Waves are everywhere around us! They are disturbances that travel through a medium or space, carrying energy without carrying matter. Here are some common examples:

• Sound waves: These are how we hear. They travel through the air, water, or solids.
• Light waves: This is how we see! Light is part of the electromagnetic spectrum, which also includes radio waves used for communication.
• Water waves: Think of ripples in a pond or ocean surface waves at the beach.
• Earthquake waves: These are powerful waves that travel through the Earth's crust during an earthquake.

Measuring a wave's length

A sine wave has a repeating pattern. The length of one full pattern is what we call the wavelength. You can find the wavelength by measuring the distance from one peak (the highest point) of a wave to the very next peak. You can also measure from one trough (the lowest point) to the next trough, or from any point on the wave to the next identical point where the pattern starts to repeat.

Waves have other important features too:

• Frequency: How many wave cycles pass a point in one second.
• Amplitude: The height of the wave from its middle point to a peak or trough. This tells you how strong the wave is.
• Phase: Where a point on the wave is in its cycle.
• Speed: How fast the wave travels.

The symbol most often used for wavelength is the Greek letter lambda (λ).

Images for kids

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  Wavelength changes when a wave moves into a different material.

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  Colors separating as light passes through a prism.

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  A wave moving through a changing material.

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  How a wave on atoms can be seen with different wavelengths.

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  A group of waves traveling together.

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  Light patterns from two slits.

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  The pattern created when light passes through two narrow openings.

See also

In Spanish: Longitud de onda para niños