Diffraction vs Refraction

In this new video, we’re going to take a look and see what are the differences between energy and matter. We've said earlier that chemistry is just the study of matter and the physical or chemical changes it undergoes. Matter is anything that contains mass or takes up space. But we’re going to say that light and matter, although very similar, behave differently.
First things first, we're going to say that light and matter travel differently as they pass from one medium to another medium/ we’re going to say light travels at a different speed as it goes from air to water. As you can see here, we're going to say our light particle is here and it shines through and hits the surface of the water. It makes a sharp change in direction. This phenomenon is known as refraction. This refraction is very different from the way matter behaves. If you took a stone or a pebble and you threw it into the pond, it will gradually change its speed.
Light on the other hand sharply changes its speed because of refraction phenomenon. That’s one major difference between light and matter. They change directions at different speeds as they go from one medium, which is air to a new medium which is water.

We’re also going to say light passing through the opening of a slit creates a semi-circle wave in a phenomenon known as diffraction. We're going to say that matter does something different. The way light can travel, light can travel as a wave and this wave’s eventually going to hit the opening of this slit and come out the other side. As it comes out the other side, it comes out as a semi-circle. This is known as diffraction. Matter on the other hand travel in this way and will come out the other side not as a semi-circle but in this fashion right here. That's yet another difference between light and matter.

Finally, we’re going to say if two light waves pass through adjacent slits, then these semicircle waves can react with each other. They could react in two different ways. We could say when they come out, remember light can travel as a wave. We can say that they come out in a way where they lineup perfectly with each other. We're going to say that here, the crests match up perfectly, the troughs or the bottom of the hills match up perfectly. What is this going to do? This is actually going to make them combine together in a phenomenon known as constructive interference. When the crests match up perfectly or the troughs match up perfectly, you have two waves. It’s called constructive interference. This is just going to basically double the height of the wave. It’s going to create a new wave that is nearly twice as high because it's basically adding both waves together. We're going to say constructive interference since it's increasing the height by so much, the height of the wave. We’re going to say that it increases our amplitude.
Something else could happen. The two waves instead of combining together could wind up destroying one another. This happens when they don't match up perfectly. Here, the crests don't match up perfectly. Here, it's the crest and the trough matching up. These actually destroy one another. For them to add up together, a crest and a crest must match up with a trough and a trough. But here, it's the opposite. A crest is matching, or the high point of the wave is matching up with the low point of the wave which is called the trough.
This actually causes them to destroy each other. Instead of them adding up together, we're going to get no wave at all the end because both waves wind up destroying one another. We're going to say this is destructive interference. Since we destroyed the wave, the amplitude gets destroyed too. We're going to say there's going to be no amplitude anymore. The amplitude disappears because the wave disappears. Just remember, matter is just anything that possesses mass and takes up space. Mass and energy, although similar, they’re different.