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 three times ten to the eight meters per second when they're in different mediums though they'll 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 into 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 at 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 colors that we can see now one of the slightly annoying things about this topic is that you need to memorize 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 and work your way outwards if you don't know the colors of the rainbow already you can remember them as roy g biff or red orange yellow green blue indigo and violet after violet comes ultraviolet which makes sense and before red is infrared so i hope 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 hope you enjoyed it and i'll see you next time