General Properties of WAVE Name: ____________________ ( ) Class: _____ Date:_____________ General Properties of WAVE Sec 3 Exp Science PHYSICS (c) CSS

Name: ____________________ ( ) Class: _____ Date:_____________ What is a Wave? Wave is a mechanism that carries energy from one point to another. A wave is created by vibrations or oscillations of objects or substances. Waves carry energy from one point of vibrations or oscillations to another. (c) CSS

Name: ____________________ ( ) Class: _____ Date:_____________ 2 Types of Waves TRANSVERSE LONGITUDINAL (c) CSS

Name: ____________________ ( ) Class: _____ Date:_____________ Transverse waves Waves that travel in a direction perpendicular to the direction of vibration of particles. This means that particles of transverse wave only moves up and down, while wave travel sideways. Some examples are rope waves, water waves, light waves and radio waves. Direction of wave (c) CSS

Name: ____________________ ( ) Class: _____ Date:_____________ Transverse Wave Transverse wave in air. Direction of wave is from left to right. Notice how the air particles are vibrating with respect to the direction of wave motion. The air particles are just vibrating up and down about their fixed positions as the wave moves from left to right. (c) CSS

Name: ____________________ ( ) Class: _____ Date:_____________ Longitudinal Waves Waves that travel in the same direction as the direction of vibration of particles. Particles of longitundinal waves move side-to-side in a direction parallel to direction of wave. Some examples are sound waves and waves produced by springs. Direction of wave (c) CSS

Name: ____________________ ( ) Class: _____ Date:_____________ Longitudinal Wave Longitudinal wave in air. Direction of wave is from left to right. Notice how the air particles are vibrating with respect to the direction of wave motion. Although it appears at first glance that groups of air particles are moving from left to right, if you look closely, the air particles are in fact just vibrating about a fixed position. (c) CSS

Key point 1! for ALL wave motion Name: ____________________ ( ) Class: _____ Date:_____________ During wave motion, the particles are NOT transferred from one point to another. They just vibrate about their fixed or neutral position. (c) CSS

Name: ____________________ ( ) Class: _____ Date:_____________ Terms used in waves Crests Troughs Displacement Amplitude Wavelength Frequency Period Wavefront (c) CSS

Name: ____________________ ( ) Class: _____ Date:_____________ Displacement /m Crests wavelength amplitude Distance/m amplitude wavelength Troughs (c) CSS

Properties of Wave Motion Name: ____________________ ( ) Class: _____ Date:_____________ Properties of Wave Motion Crest: The highest point of a transverse wave. Trough: The lowest point of a transverse wave. Amplitude: Maximum displacement from rest or central position. Unit: meter (m). Displacement has positive and negative values. Normally when particles moves upwards it’s positive. When downwards its negative. (c) CSS

Name: ____________________ ( ) Class: _____ Date:_____________ Describing a wave: Wavelength: Shortest distance between two ( λ ) points on the wave that are in phase. Unit: meter (m) Distance between two troughs. Distance between two crests. (In phase = both particles move in the same direction, at the same speed and have the same displacement from rest position.) (c) CSS

Name: ____________________ ( ) Class: _____ Date:_____________ Describing a wave: Frequency: Number of complete waves ( f ) produced in one second. Unit: Hertz (Hz) Period: Time taken to produce one ( T ) complete wave. Unit: seconds (s) Inverse of frequency (i.e. T = 1 / f ) (c) CSS

Name: ____________________ ( ) Class: _____ Date:_____________ Describing a wave: Wave speed: The distance travelled by a wave (v) in one second. SI unit: m /s Wavefront: An imaginary line on a wave that joins all points which have the same phase of vibration. (c) CSS

Name: ____________________ ( ) Class: _____ Date:_____________ Quick Check A boy sings as he plays with a rope. He vibrates one end of the rope up and down repeatedly, while the other end is fixed to a wall. What type of wave is obtained in the rope? Transverse Define transverse wave. A wave where its particles vibrate in a perpendicular direction to that of the direction of wave. (c) The sound that the boy made while singing is an example of (transverse, longitudinal) wave. (c) CSS

Name: ____________________ ( ) Class: _____ Date:_____________ Quick Check Give one example of a longitudinal wave. Sound wave 3. Label the wave terms – crest, trough, wavelength and amplitude in the displacement-distance graph below of a transverse wave. (c) CSS

Relationship between velocity, frequency and wavelength Name: ____________________ ( ) Class: _____ Date:_____________ Relationship between velocity, frequency and wavelength Speed of a wave = frequency of wave X wavelength of the wave In symbols, v = f  v = wave speed/velocity (m/s) f = frequency (Hz)  = wavelength (m) (c) CSS

The frequency – period equation Name: ____________________ ( ) Class: _____ Date:_____________ The frequency – period equation f = 1/T Knowing frequency, we can find the period of a wave. Similarly, if we know the period, we can find the frequency of the wave. (c) CSS

Name: ____________________ ( ) Class: _____ Date:_____________ The Ripple Tank The ripple tank allows us to observe the behaviour of waves easily. Basically waves behaves similar to that of light: Waves reflect Waves refract (c) CSS

Name: ____________________ ( ) Class: _____ Date:_____________ Measuring wavelength 1 wavelength (c) CSS

Displacement vs distance Graph Name: ____________________ ( ) Class: _____ Date:_____________ Displacement vs distance Graph Waves can be plotted on a displacement vs distance graph. The displacement refers to displacement of particles, while distance refers to the distance of particles from a starting point. From this graph, we can find: Wavelength Amplitude Distance of particles from a position (c) CSS

Name: ____________________ ( ) Class: _____ Date:_____________ Displacement /m wavelength amplitude Distance/m amplitude wavelength (c) CSS

Displacement vs time Graph Name: ____________________ ( ) Class: _____ Date:_____________ Displacement vs time Graph Waves can be plotted on a displacement vs time graph. The displacement refers to displacement of particle just one particle, while time refers to the time of that same particle moves a particular displacement From this graph, we can find: Period of wave Amplitude From period, we can calculate the frequency of the wave (c) CSS

Name: ____________________ ( ) Class: _____ Date:_____________ Displacement /m period amplitude Time/s amplitude period (c) CSS

Eg. Displacement vs time Graph Name: ____________________ ( ) Class: _____ Date:_____________ Eg. Displacement vs time Graph A displacement – time graph of a wave with wavelength 0.4m is shown. Calculate the frequency of the wave. Period of wave is 0.5 s So f = 1/T = 1/0.5 = 2 Hz (b) Calculate the speed of the wave. Speed = frequency x wavelength = 2 x 0.4 = 0.8m/s (c) CSS

Name: ____________________ ( ) Class: _____ Date:_____________ Displacement /m 0.25 0.5 0.75 1.0 Time/s (c) CSS

Name: ____________________ ( ) Class: _____ Date:_____________ Quick Check Calculate the wave speed of a wave of frequency 500 Hz and a wavelength of 0.02 m. v = 500 x 0.02 = 10 m/s Calculate the wavelength of a wave that has a frequency of 2kHz and speed of 5m/s. wavelength = v/f = 5/2000 = 0.0025 m (c) CSS

Name: ____________________ ( ) Class: _____ Date:_____________ Quick Check A wave of speed 330 m/s has a wavelength of 2m. Calculate the frequency of the wave. frequency = v/wavelength = 330/2 = 165 Hz (b) Calculate the period of the wave. period = 1/f = 1/165 = 0.006 s (c) CSS