In today's video, we're looking at the electromagnetic spectrum, which is this entire range of electromagnetic waves, and we'll cover both where they come from and what happens when they're absorbed. The first thing to know is that electromagnetic, or EM waves, are all transverse waves, which means that they oscillate perpendicular to the direction of energy transfer. so up and down, and when they're in a vacuum they'll all travel at exactly the same speed of 3 times 10 to the 8 meters per second. When they're in different mediums though, they will travel at different speeds and this can lead to a fraction, which is where the wave changes direction. As you can see in our table, we split electromagnetic waves.
and seven basic types, but they're actually all part of one continuous spectrum. What differentiates them is their wavelength and their frequency, which are inversely related, which means that if one goes up, the other one goes down. So if you read the table from left to right, the frequency increases while the wavelength decreases. So radio waves have the biggest wavelength but the smallest frequency, and gamma rays have the smallest wavelength but the biggest frequency. And to give you a rough idea of the wavelengths, they vary from multiple kilometers for radio waves to less than a thousandth of a nanometer for gamma rays.
As human beings though, our eyes are only able to detect a tiny part of the spectrum which we call visible light and the different wavelengths within this region are what give us all of the different colours that we can see. Now one of the slightly annoying things about this topic is that you need to memorise the order of all the different waves in the spectrum. Personally I think the best way to do this is to start in the middle with visible light work your way outwards. If you don't know the colours of the rainbow already, you can remember them as ROY, G, BIF, or red, orange, yellow, green, blue, indigo and violet.
After violet comes ultraviolet, which makes sense, and before red is infrared. To help you remember that X-rays and gamma rays are over on the right, remember that all of these types, so ultraviolet, X-ray and gamma, can all be ionizing and cause damage to our cells, so they're grouped together. Then all we have left are microwaves and radio waves, which are both used in communication, and go on the far left. The last thing we need to cover is where electromagnetic waves come from. The short answer is that they come from everywhere.
Don't worry about remembering the exact details, but to give you some idea, radioactive decay can cause gamma rays to be emitted, while visible light, ultraviolet and x-rays can all be emitted when electrons drop down energy levels. And when the bonds that hold molecules together vibrate. it can generate infrared radiation.
So really, radiation is emitted from all over the place, by loads of different things. Once they've been emitted, all of these waves can then travel across the universe, through empty space, and when they come into contact with something, they can be either reflected, absorbed, or transmitted, or sometimes a combination of these three might happen. For example, some waves might be reflected, but other waves might be absorbed. Anyway, that's everything for this video, so I hope you enjoyed it, and I'll see you next time!