Hi, I'm Sean Tvelia and we're here at Suffolk County Community College to look at some easy physics projects with refraction. Refraction is a change in direction of a wave as a result of entering a medium of a different refractive index. Today I have a simple green laser pointer and a number of objects that we can show how light interacts with as it moves through the material. As a laser pointer obviously it's going to start out moving through air and it will move through each one of these different materials starting with water, a heavy liquid, some mineral oil and some acrylic. As we move the laser pointer through the water, we can see that in one direction it enters the water at an angle of incidence and the angle of refraction is different. It changes as it enters the water. If we move the laser pointer to the heavy liquid, because this liquid is more dense than water, the index of refraction is greater and we can see a greater angle in the laser in the liquid. In real life refraction helps us to be able to see things and we can look at that with this demonstration where I can use a Pyrex glass rod and some simple mineral oil. Because the mineral oil has the same refractive index as the glass rod as light moves through the beaker and into the glass rod, there is no refraction and as a result the glass rod will appear to disappear. With acrylic, we can demonstrate refraction and again with the laser pointer, as the laser moves through air and into the acrylic, we'll see that the laser bends into the acrylic as a more dense material and using complete internal refraction we can actually have a laser pointer move through a curled object. And that's refraction.