waves one of the first things we need to know about waves is there are two different types of wave one shown here by waves in the sea and the other one shown by sound waves so how are they different well first let's look at the sea waves if we look at them represented with this Slinky we see that the vibrations are at 90° or perpendicular to the direction of travel of the wave these are called transverse waves and examples of them are waves in water waves on a string or light waves now let's look at the sound waves again again we see them represented by the slinky but this time the direction of vibration is parallel to the direction of travel these are called longitudinal waves and the only example you really need to remember is sound one really important thing to remember about waves is they only transfer energy from place to place not any matter and we can see that here by looking at a lovely rubber duck sat in a bath as a wave goes through the duck Bobs up and down but once the wave's gone he's back to his original position the wave has carried energy through but it did not carry the duck with it finally we need to know some key features of waves first off wavelength a wavelength is the length of a full cycle of a wave from one point to the next same point it's easiest to think of as a distance from Crest to Crest or from trough to trough and we measure it in meters and it's given the symbol Lander a nice Greek symbol the amplitude is like the size of a wave but we need to remember that it's measured from the equilibrium position or the central line to the crest not from the crest to the trough find frequency which is the number of complete waves to pass a point every second and it's given the unit of Hertz so an example of this would be if 10 waves pass in 2 seconds the frequency would be 5 Hertz using these things we can actually now calculate the speed of a wave us using the equation speed equals frequency time wavelength or to give it in symbol form V equals F Lambda so there's a lot to learn here but once you've learned these Core Concepts it will give you much more confidence in the rest of the topic