230 likes | 363 Views
KS4 Waves: Wave Character. Energy and Waves : Introduction. Waves carry energy from one place to another. There are 2 main types of wave you need to know about:. Transverse Waves e.g. light waves. Longitudinal Waves e.g. sound waves. Waves : Introduction. TRANSVERSE WAVES.
E N D
Energy and Waves : Introduction Waves carry energy from one place to another. There are 2 main types of wave you need to know about: Transverse Waves e.g. light waves Longitudinal Waves e.g. sound waves
Waves : Introduction TRANSVERSE WAVES Make a transverse wave using a rope between two people like this : What type of energy is the wave transferring? In which direction is the energy moving? • In which direction is each part of the rope moving? [put a marker on the rope to help you see] kinetic
Waves : Introduction TRANSVERSE WAVES You should have noticed that each part of the wave moves at right angles [90º] to the direction the energy is moving in: Particle Movement Energy Movement Make a labelled diagram of your rope like this :
Waves : Introduction TRANSVERSE WAVES Crest / Peak a Displacement+ Time a Trough
Wavelength and amplitude What is the wavelength () of a transverse wave? It is the distance between two consecutive points on the wave. What is the amplitude (a) of a transverse wave? It is the half-height of the wave, the bigger the amplitude of the wave, the more energy it has.
Animation to demonstrate wavelength, amplitude and frequency
Waves : Introduction LONGITUDINAL WAVES Make a longitudinal wave using a spring between two people like this : What type of energy is the wave transferring? In which direction is the energy moving? In which direction is each part of the spring moving? [put a marker on the spring to help you see] kinetic
Waves : Introduction LONGITUDINAL WAVES You should have noticed that each part of the wave moves in the same direction as the direction the energy is moving in: particle movement energy movement When you speak to someone, the air vibrates as a longitudinal wave :
Waves : Introduction LONGITUDINAL WAVES Make a labelled diagram of your spring like this : Compression Compression Rarefaction Rarefaction
Transverse or longitudinal? light sound p-waves water s-waves ultrasound ultraviolet light ultrasound sound water p-waves s-waves ultraviolet
Waves : Frequency The number of waves passing a point each second is called FREQUENCY [ƒ] Frequency [ƒ] is measured in hertz [Hz] Frequency [ƒ] = Number of waves passed Time [s] 1 wave per second = 1 Hz If the wave below passes a point in 1 second, what is it’s frequency?
Waves : Frequency Complete the table 6 3 5 10 0.5 1
Waves : wave speed Imagine waves on the sea travelling over a shipwreck: = 2m 1 second later :
Waves : wave speed In the diagram, 5 waves pass the shipwreck in 1 second………………….so the frequency = 5 Hz The wavelength [] = 2 m This means that the waves travel 10 m in 1 s ……….………………so the speed is 10 m/s So, in this example, the frequency X wavelength = speed 5 X 2 = 10 Hz m m/s This is usually written as :
Waves : wave speed V = x For the Higher Tier papers, you will need to be able to change the subject of the formula : = V and = V
Formula triangles Formula triangles help you to rearrange formula. The triangle for the wave equation is shown below: Whatever quantity you are trying to find cover it up and it will leave you with the calculation required. …and you are left with the sum… So if you were trying to find frequency, f….. f = v v …you would cover f up… f x
Wave Speed – complete the table 3.0 0.2 1.32 2.4 0.01
Energy and Waves : A Question The photograph shows waves travelling across the surface of a pond. 1m 1) Is this an example of a transverse or longitudinal wave? 2) Estimate the wavelength of the wave: 3) If the frequency of the wave is 0.2 Hz, calculate the speed of the wave: transverse 0.15m 0.03m/s
Ultraviolet Water Light Sound Which wave below is a longitudinal wave?
Metres Hertz metres Hertz/metres Hertz What are the units of frequency?
1.2 m/s 0.88 m/s 3.0 m/s 30 m/s A wave has a wavelength of 6m and a frequency of 5Hz. What is the speed of the wave?