What is Infrared Light? William Herschel's Amazing Discovery of Infrared Radiation and Waves - 02

What is infrared light? Here we will learn the story of William Herschel and how he completely by accident discovered infrared light. Infrared Radiation (IR) was unknown in his time, but now we know that the IR spectrum is just a small part of the broader electromagnetic spectrum. Herschel discovered infrared radiation by measuring the temperature of different parts of the visible light spectrum made by passing sunlight through a prism. He discovered that just beyond the red part of the spectrum were invisible infrared waves. Now we know that the definition of infrared light is just longer wavelength waves in the EM spectrum. We also now know that infrared rays are associated with heat and that the infrared frequency range is just beyond that of the red light in the visible rainbow. --------------- Hello welcome to smarter in science we're going to take a few minutes of your time and learn together about something truly amazing in the realm of science. Today we're going to talk about the amazing discovery of infrared radiation. There's a really cool story behind infrared radiation and how it was discovered i'm going to share that with you today. The first thing is let's talk a little bit about what is infrared radiation and that is basically the type of light in type of invisible light that we associate with heat is given off by an object. so here are a couple of examples of that here's a space shuttle that's just coming from the atmosphere it's gotten very very hot notice the underside of the ship is kind of as the reddish colors and the whitest the whitish color is where the top of the ship is blue bullish colors. so what this means obviously the bottom of the ship hotter and when something is hotter it radiates more infrared radiation and so those why the coat that's why the colors are red there where is the top of the ship is not as hot and in this picture is represented by blue because it's not radiating as much in the infrared there on the top of the ship. here's a picture of a house and you can see sort of the same thing here most of the house for instance the the the roof here is a bluish color that means that there's not very much heat coming out of the roof there it's nicely insulated there but the ridgeline here at the top of the house the windows the doors things like that it's very hard to insulate those so you see the heat coming through the windows and the doors and that's why you see the red there because the heats coming from the inside of the house out you see that in the infrared. Ok as I said before the discovery of how this radiation behaves and how it was discovered two stories really really neat and we're going to talk about that right now. So I'd like to introduce you to somebody if you've never heard of him he's a famous scientist whose name's William Herschel lived from 1738 1822. Now this picture of our sun is a modern picture of course Herschel never saw the Sun as it is in this picture here from this from a high-powered telescope or satellite as we see it today. Basically he spent a great deal of time studying light from the stars with the telescope that he used in his day and what he did one of the things he did was he was put these filters in front of the telescope different color filters. red filters yellow filters blue filters to a basically filter the light coming from the Sun so that he could study in his telescope and just from the interaction with the telescope he started to realize that he thought the red light from the Sun when he would isolate the red light seemed to be hotter than the other colors as he would isolate them with his filters now this wasn't a scientific experiment this was just something he was noticing so he decided to investigate further. now even back in Herschel today the scientists of the time were well aware that sunlight can be broken down with composed of a whole host of colors of the rainbow there and he knew all about prisms that could do that job. So he knew that sunlight was a mixture of all the colors of the rainbow and he knew that he could take white light and split it up into the different colors violet indigo blue green yellow orange and red so what he wanted to do with scientifically see if any of these colors coming from the Sun actually had a higher temperature or did they all behave the same. So in order to do that he decided to set up an actual experiment to test and see if they were all the same or any of the colors were hotter or colder than any of the other ones. now here's what we have a sort of an artist rendition of him of a personal in his laboratory and you can see the sunlight coming in being split by the prism and form a rainbow down here now. in 1800 he devised his experiment to see if the different colors of the rainbow actually had different temperatures, and along the way he completely by accident discovered infrared light.