Refraction, Dispersion & Diffraction Video

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  • 0:00 What Are Light Waves?
  • 1:08 Refraction
  • 2:25 Diffraction
  • 3:12 Dispersion
  • 3:47 Lesson Summary
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Lesson Transcript
Instructor: David Wood

David has taught Honors Physics, AP Physics, IB Physics and general science courses. He has a Masters in Education, and a Bachelors in Physics.

Learn about light waves and how they can be affected by objects. Explore the difference between refraction, dispersion, and diffraction. Take the quiz to see how much you can remember.

What Are Light Waves?

In this lesson we're going to talk about refraction, diffraction, and dispersion. These are three things that can happen to light waves. But first we should define what we mean by light waves. A light wave is an electromagnetic wave, which is a wave made up of alternating electric and magnetic fields. In everyday life, when people talk about light waves, they usually mean visible light. But visible light is only one part of the electromagnetic spectrum, along with radio waves, infrared, microwaves, ultraviolet, x-rays, and gamma rays. Physicists call all of these things light waves.

There are a lot of fun things you can do with light waves. You can break them into individual colors, cause them to bend or spread out, or manipulate them to do clever magic tricks. Light waves are also super important because we wouldn't be able to see without them.

Let's talk about some of the effects that light waves undergo.


Refraction is simply the bending of light when it moves from one material into another. If light is beamed at 90° to a surface, no bending happens. But if you shine the light at an angle, it will bend one way or another. The way it bends depends on the density of the materials of both the source and the surface it's hitting, and the different density of the material the light started in versus the material it ended in is the cause of refraction.


Think of a beam of light as being like a series of wave fronts, represented as lines. Shining the light at an angle causes one side of the wave front to reach the new material before the other side. Light travels more slowly in a more dense material, so this causes one side of the wave front to slow down or speed up before the other, and this makes the light bend.

Refraction of Wave Fronts

If the light moves from a low-density material to a high-density material, the light will bend towards the normal, or in other words, towards a line that runs 90° to the surface. If the light moves from a high-density material to a low-density material, the light will bend away from the normal. And that's pretty much it, everything you need to know about refraction.

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