in this video we will be looking at GCSE physics topic six and that is waves here are some of the subtopics we're going to be looking at throughout this video as always these pages will be available on my Etsy page which is linked in the description thank you very much for watching and I hope you enjoy first of all we have wave Basics I thought I'd include this just as an introduction to waves so waves transfer energy in the direction they are traveling all waves can be absorbed transmitted or reflected particles vibrate to transfer energy when waves pass through a medium so a medium is just the same as like a material or a substance couple equations that'll be useful to remember time period equals 1 over the frequency so tal 1 / f and also wave speed equals frequency time wavelength and again V equal f * Lambda which is the symbol for wavelength here next we have transverse and longitudinal waves these are the two types of waves that you will come across at GCSE so on the left hand side a transverse is probably what we'd normally associate with a regular wave if someone said to you what is a wave this is what you'd think of so a couple of key things that you need to remember about the transverse wave include the amplitude which is the height of the wave from the rest position next is the wavelength that is the point on one wave to the same point on the next wave it is the distance between that we have a Crest or a peak which is the top of the wave and the trough which is the bottom of the wave if you can remember exactly what those four things are you'll be absolutely fine when it comes to labeling a transverse wave now a slightly more complicated idea is that transverse waves have perpendicular vibrations to the direction of the energy transfer I wouldn't worry too much about remembering exactly what that means but just remember that it's perpendicular for transverse waves because you'll find that in a minute longitudinal waves are parallel most waves are transverse such as electromagnetic waves or EM waves and also water waves so moving on to longitudinal waves they have parallel vibrations to the direction of the energy transfer just means they kind of vibrate in line with which direction the transfer is going and some examples include sound waves in air and also seismic shock waves so a longitudinal wave looks slightly different but it is rare faction and compression is just a series of that so rare faction is what we call the separation when it gets like wider apart and compression is when a lot of the parts within the wave become very close together which kind of makes sense and then wavelength here is kind of like the gap between two rare factions or two compressions moving on to refraction so refraction don't get this confused with reflection reflection is simply when it just bounces off of a flat surface but refraction is typically when the waves will change direction at a boundary between two mediums as you can see the definition I've written just there so the way we show this there's two ways really so a wave front diagram which you may have seen before make sure you remember that this is called a wave front diagram because often in exams and I've foolen for this before I didn't remember what a wave front diagram was and it said to draw one and I couldn't remember so I lost the marks on that so as long as you remember that this is a wave front diagram basically what I would recommend is draw the normal line that goes all the way through so that line that goes behind the waves through the middle will always be perpendicular to the surface of the medium so as you can see when that denser material comes along in my diagram the normal line is changing to be at a slight angle and the waves will always be perpendicular to that line so it makes it a lot easier to draw when you're trying to work out how it's going to look and then next we have a normal ray diagram so I've drawn two examples here you've got the line going in from the bottom left this is just a normal Ray approaching the crossing between two materials or mediums so material one now when you cross along that line I've drawn a normal line at exactly the point where it will cross through from Material one to material 2 after that line if material 2 is denser the ray will bend towards that normal line so think of it like the angle will basically just be smaller so the angle of incidence is the one going into the normal line and as you cross into material 2 the angle of refraction is what we call the kind of outgoing Angle now if material one is denser so you're going from a more dense material to a less dense material the angle of refraction will be bigger than the angle of incidence it's a lot harder to think about when you hear it in words just kind of look at that diagram you probably will get the idea but that is one key thing to remember and often in exams you will not have the normal line drawn for you so you may have to do that as well it will always be perpendicular to the line between the material one and material 2 the final little section on this topic is electromagnetic waves so there are plenty of very very good YouTube videos that talk about electromagnetic waves if you look up after this video just look up the electromagnetic wave song and you will be able to remember every single one of these in order in the next 5 minutes so so radio waves micro waves infrared visible light ultraviolet X-rays and gamma rays I still remember the song from when I did my gcses and that was six seven years ago now so as those electromagnetic waves go along the wavelength is decreasing and the frequency is increasing now those numbers that I've written underneath just indicate the wavelengths of each of those things so you can see radio waves have a wavelength of roughly anything between a meter and 10 4 M which is 10,000 M microwaves are 10us 2 m so that's kind of like 10 10 mm kind of thing infrared 10us 5 so then you're talking 10 micrometers and then it just gets smaller and smaller from there so EM waves are transverse waves as we talked about before that transfer energy from a source to an absor absorber all electromagnetic waves travel the same speed through air or vacuum and that speed is the speed of light which just in case you need to know it it is 3 * 10^ 8 m/s so that's 300 million m/s the human eye can only detect the visible light portion and different EM waves have many different uses as we're going to talk about on the next slide so the uses of EM waves it's not the most exciting of slides but it is just information that you need to remember I've tried to cut down a lot of the waffle that the textbooks contain and literally just bullet point them for you so radio waves radio communications make sense Bluetooth and TV they're kind of all fall under the radio communication but useful in case you need to know it microwaves microwave ovens and also satellites infrared used to monitor temperature things like thermal cameras and heaters so you you've probably seen like a thermal camera where all the different colors are like red and blue depending on the heat around it visible light so fiber optics these are basically like wires that carry data this is what's used in things like Advanced Wi-Fi and Big Data cables that travel all under the oceans and stuff like that ultraviolet things like sun ttans invisible pens so sometimes you might have seen those pens before where you write a hidden message and then you use a light to see that message that's ultraviolet and also fluorescent lights x-rays medicine in radiography so X-rays and also radiotherapy and finally gamma rays medical tracers so this is something that can be injected into someone and it can latch onto a certain type of cell that they want to track and it will provide information to the doctors and stuff like that about that stuff and the final slide is dangers of EM waves so radiation risk can be measured using the dose in CTS high frequency waves transfer lots of energy so can be harmful so so those high frequency waves include UV X-rays and also gamma rays so the ones at the right hand side of our electromagnetic spectrum that we looked at before on the other hand low frequency waves such as radio waves do not transfer much energy and pass through soft tissue without absorption so these things are probably going through our bodies all the time because of radio signals and things like that that can be received through things such as our mobile phones UV radiation such as radiation that comes from the sun damages surface cells if it's exposed too much which can lead to sunburns and also could increase your chances of skin cancer so always make sure you use Sun cream and all that stuff and that is the end of topic six waves our next topic will be magnetism and electromagnetism please like And subscribe if you found it useful thank you very much for watching and I will see you in the next video