WAVE TERMS BUTTONS Click here Clicking here will

WAVE TERMS BUTTONS Click here: Clicking here will move you to the page. clicking Clicking here will here bring reveal will you reveal some back an information. to answer. a next this page. Clicking here on here me will allow take you you toto to hear a. SIback list multipliers some of equations, information table. Clicking on the topic. here. Clicking againwill here return take again you will back tostop your to the previous sound. previous page. TOPICS Jump to… …describing waves and the wave equation (2 pages). Jump to… …transverse and longitudinal waves (3 pages). Jump to… …the ripple tank (1 page). Jump to… …reflection and refraction (3 pages). Jump to… …measure the speed of a water wave (2 pages). Jump to… …practice question (1 page). Jump to… …exam questions (2 pages).

DESCRIBING WAVES Wavelength Amplitude Crest and Trough Frequency Speed Rest position

DESCRIBING WAVES Wavelength Amplitude Crest and Trough Frequency Speed Wavelength Length of one wave (metre) Rest position

DESCRIBING WAVES Wavelength Amplitude Crest and Trough Frequency Speed Amplitude The maximum displacement Rest position

DESCRIBING WAVES Crest is the highest part of a wave Wavelength Amplitude Crest and Trough Rest position Frequency Speed Trough lowest part of a wave

DESCRIBING WAVES Wavelength Frequency Number of waves passing every second (hertz) Amplitude Crest and Trough Rest position Frequency Speed 2 hertz 1 hertz 0. 5 hertz

DESCRIBING WAVES Wavelength 0. 4 metre speed = = Amplitude Crest and Trough Frequency Speed = distance time 0. 4 m 2 s 0. 2 m/s Rest position

WAVE EQUATION The properties wave speed, frequency and wavelength come together in the wave equation. This states that the wave speed, v, is equal to the frequency, f, times the wavelength, , (lambda) wavelength in metres, m wave speed in metres per second, m/s UNITS frequency in hertz, Hz (waves per second) v=f The wave triangle gives the equations: v = f. or f = v / or = v / f The frequency (f) of a note on a piano is 256 Hz. It has a wavelength ( ) of 1. 3 m. How fast will the sound wave move through the air? Wave speed v = f. = 256 Hz x 1. 3 m = 332. 8 m/s Notice from the previous slide, that as you increase frequency, the wavelength gets smaller. The frequency is inversely proportional to the wavelength. This means that if the frequency doubles, the wavelength halves.

TRANSVERSE WAVES Rope oscillations go up and down. The wave carries energy from one place to another. The wave carries energy to the right. In a transverse wave, the particles of the wave move up and down at right angles to the direction of travel of the wave. Water waves and the waves of the electromagnetic spectrum are transverse waves.

LONGITUDINAL WAVES wavelength Y don yn cludo egni i’r dde. In a longitudinal wave the particles move to and fro in the same direction as the direction of travel of the wave. The wavelength of a longitudinal wave is the distance between one compression and the next. Sound waves are longitudinal waves.

WAVE GRAPHS Displacement from rest amplitude distance along the wavelength A graph of the whole wave Displacement from rest amplitude time for one complete oscillation Graph of one particle

THE RIPPLE TANK light source tray of shallow water pattern of waves on a screen plane wave fronts Move the plane wave. The arrow shows the direction of travel of the waves. This is at 90° to the wave fronts. We can’t see this.

REFLECTION normal Direction of travel of the wave pla ne ve wa nt fro s angle of incidence reflection r i angle i = angle r barrier When waves are reflected, only the direction of movement changes. There is no change in wave speed, frequency or wavelength Waves reflecting Reflection terms

REFRACTION Wavelength longer DEEPER WATER FASTER speed NO change in frequency Wavelength shorter Wavelength SHALLOW WATER speed DŴR SLOWER B S – LLAI DWFN NO change in frequency Frequency Speed Waves bending Wavelength longer NO change in frequency DEEPER WATER FASTER speed

REFRACTION TERMS normal The direction of travel will not change if the angle of incidence is zero. In refraction, the speed and the wavelength always change. The frequency remains constant. DEEPER WATER angle of INCIDENCE i When it slows the direction of travel of the wave moves towards the normal. angle of REFRACTION r As it gets faster the direction of travel of the wave moves away from the normal SHALLOWER WATER DEEPER WATER

WATER WAVE SPEED EXPERIMENT 40 cm : CALCULATING SPEED GRAPH stop watch tray Water Depth (cm) Time for wave to travel 3 lengths of the tray. Total distance of 120 cm = 1. 20 m (s) Mean speed (m/s) 1 2 3 Mean time 0. 5 5. 50 5. 39 5. 46 5. 45 0. 22 1. 0 4. 60 3. 75 4. 02 0. 30 1. 5 3. 27 3. 19 3. 60 3. 35 0. 36 2. 0 2. 88 3. 12 3. 19 3. 06 0. 39 2. 5 2. 49 2. 58 2. 61 2. 56 0. 47 3. 0 2. 27 2. 36 2. 45 2. 36 0. 51 speed = distance time = 3 x 0. 40 mean time = 1. 20 m 5. 45 s = 0. 22 m/s

wave speed m/s SPEED – WATER DEPTH GRAPH EXPERIMENT 0. 6 0. 5 0. 498 0. 4 x 2 0. 3 0. 255 0. 2 x 4 0. 1 0 0 0. 75 cm 1 0. 5 3. 0 cm 1. 5 2 depth of water, cm 2. 5 3 3. 5 Water Depth (cm) Mean speed (m/s) 0. 5 0. 22 1. 0 0. 30 1. 5 0. 36 2. 0 0. 39 2. 5 0. 47 3. 0 0. 51

PRACTICE QUESTION Click on the correct squares only in the grid; amplitude wavelength amplitude wavelength

EXAM QUESTION 1 This is one wave WJEC: Physics 1 June 2016 (Found. ) Q. 4 6 speed = frequency x wavelength = 40 Hz x 120 m = 4800 m/s 8 40 Hz means that 40 waves are passing every second. 4800 speed = distance time = 200 m/s = 150000 m 750 s

EXAM QUESTION 2 WJEC: Physics 1 June 2018 (Found. ) Q. 6 (High. ) Q. 1 In a transverse wave the oscillations are at right angles to the direction of travel of the wave. (ii) Chris suggests that if the depth of water increases four times, the wave speed doubles. Use data from the table opposite to explain whether or not this statement is true. [2] The statement is true. 3. 13 1. 0 1. 22 x 4 x 2 5. 85 4. 0 A depth of water of 1. 0 m gives a wave speed 6. 26 of 3. 13 m/s. Increasing the depth 4 times to 4 metres doubles the speed to 6. 26 m/s.

EQUATIONS r e igh h er h hig Open the file “Maths for Physics” for more about the use of mathematics in Physics.

SI MULTIPLIERS p - pico k - kilo n - nano M - mega - micro G - giga m - milli T - tera You only see the letter of the prefix on an exam paper, NOT the name. On a Foundation paper only milli, kilo and mega are used.