[Music] hi and welcome back to three sighs lessons cold UK by the end of this video you should be able to describe the differences between transverse and longitudinal waves you should then be able to state examples of these types of waves and finally you should be able to describe evidence that when waves are moving it's the wave that moves are not the medium I'm showing you here two examples of waves we've got ripples on the surface of water and we've got sound waves traveling in air all types of waves fall into one of two categories and these are transverse waves and long attitudinal waves ripples on the surface of water are an example of transverse waves where as sound waves traveling an air are an example of longitudinal waves I should point out that there are many different examples of waves and we're going to be looking at several in this topic however remember that all waves are either transverse or long that hewed nor now one key fact about waves is that always transfer energy from one place to another ripples transfer kinetic energy and sound waves transfer sound energy so let's start by looking at transverse waves for example ripples on the surface of water I'm showing you transverse wave here as you can see the wave is moving up and down scientists call these movements oscillations this arrow shows the direction of energy transfer now the key fact is that in transverse waves the oscillations are perpendicular to the direction of energy transfer and the word perpendicular means up light angles so as you can see in a transverse wave the oscillations are up-and-down but the direction of energy transfer is sideways okay we're going to look now at the second category of waves these are longitudinal ways and I'm showing you along the toodle wave here now a good example of a longer toodle wave are sound waves traveling through air sound waves travel as particles in the air move from side to side so here I'm showing you the air particles you can see that we've got regions where the articles are very close together scientists call these regions compressions in between the compressions we've got regions where the air particles are spaced out and scientists call these regions rarer functions here I've paused the wave so you can see the compressions aren't River functions more clearly now unlike with transverse waves the key feature of a longitudinal wave is that the oscillations are parallel to the direction of energy transfer and we can see that here now there is one of the key difference between transverse and longitudinal waves all longitudinal waves require a medium to travel in for example air a liquid or a solid in contrast not all transverse waves require a medium and we could look at some of those and later videos now there's one really important fact that you need to learn about waves for both whippers on a water surface on sound waves and air it's the wave that travels are not the water or the air we can see that using a slinky this shows transverse waves and this represents ripples on the surface of water the red dot shows a single point and this could represent a water molecule as you can see when the wave travels through the dot oscillates up and down but it does not travel along the medium now I'm sending longitudinal waves along the slinky this represents sound waves traveling through air the red dot represents an air particle as you can see the red dot oscillates from side to side but again it does not travel through the medium remember you'll find plenty of questions on transverse and longitudinal waves in my revision workbook and you can get that by clicking on the link above [Music]