# General Wave Properties

## Presentation on theme: "General Wave Properties"— Presentation transcript:

General Wave Properties

General Wave Properties
describe what is meant by wave motion as illustrated by vibration in ropes, springs and experiments using a ripple tank state what is meant by the term wavefront show understanding that waves transfer energy without transferring matter define speed, frequency, wavelength, period and amplitude recall and apply the relationship velocity = frequency x wavelength to new situations or to solve related problems compare transverse and longitudinal waves and give suitable examples of each

Wave Wave is the product of a vibration
Two types of wave: transverse and longitudinal

Wave During wave motion, particles vibrate about their fixed position and the waveform progresses (travels). Transverse waves: particles vibrate perpendicular to wave motion eg. Light wave, water ripple Longitudinal waves: particles vibrate parallel to wave motion eg sound wave.

Wave (Transverse Wave)
wavelength crest crest amplitude trough wavelength

Wave (Longitudinal Wave)
wavelength wavelength rarefaction compression Compression: region of high pressure Rarefaction: Region of low pressure distance pressure compression compression rarefaction rarefaction

Wave Frequency, f – number of oscillations per second <Hz>
Period, T – time taken for one oscillation <s> Wavelength,  – distance between two consecutive particles in phase. <m>

Waves Example The diagram below shows a transverse wave moving to the right. a)In which direction will the particle T and V move? b) Which particle is in phase with T? W Q R U S V X T Y

Wave (cont’d) W Q R U S V X T Y
Particle T moves upwards; V moves downwards. Particle X is in phase (in step) with particle T.

Wave Relationship between frequency, f and period, T
SI unit for frequncy, f: Hz SI unit for period, T: s

Wave Relationship between wave speed, v; frequency, f and wavelength,  SI unit for speed, v: ms-1 v = f 

Wave Example Transverse waves are produced in a long rope by moving one end from side to side. The frequency of the wave is 2Hz. a) What do you mean by 2Hz? b) What is the wavelength if the speed of the wave is 0.5ms-1?

Wave a) What do you mean by 2Hz?
Each particle on the rope oscillates 2 cycles per second b) What is the wavelength if the speed of the wave is 0.5ms-1? v = f x  0.5 = 2 x   = 0.5/2 = 0.25m

Wave The speed of the wave motion, v is related to its frequency, f and wavelength  through the equation: The frequency of the wave is related to the period of vibration, T through: v = f  f T = 1

Wave Distance/m displacement/m 2 4 6 Wavelength, = 4m v = f x 
2 4 6 Wavelength, = 4m v = f x  = 0.5 x 4 = 2ms-1 time/s displacement/m 1 2 3 Period, T = 2s Frequency, f = 0.5Hz

Wave The displacement time graph of a transverse wave is shown in the figure below. Its wavelength is 3m. Calculate the speed of the wave the time taken for the wave to travel a distance of 3000km Disp/ 10-5m 0.3 0.7 1.2 time/10-5ms 1.7 2.2 2.7

Wave a) v = f  = [1/(1 x 10-5 x 10-3) ]x 3 = 3 x 108 ms-1
Disp/ 10-5m 0.3 0.7 1.2 time/10-5ms 1.7 2.2 2.7 a) v = f  = [1/(1 x 10-5 x 10-3) ]x 3 = 3 x 108 ms-1 b) t = 3000 x 1000 / 3 x 108 = 100 s T = ( ) 10-5ms = 1 x 10-5 x 10-3 s

Wave What is a wavefront?
Source:http//www.physicscentral.com What is a wavefront? Wavefront is a line that joins all the points (usually the crests) on the wave that are in phase Wavefront is likened to the bird’s eye view of a wave. Changes in wavefront indicates changes in speed of wave or presence of underwater features

wavelength direction

Waves Frequency d Medium (density / depth etc) Speed
1 2 3 As the wave approaches a shallower region, the speed of the wave reduces due to larger resistive forces . Frequency d Medium (density / depth etc) Speed Source of vibration

This is due to the shallower sea bed near the beach
Smaller wavefronts as the wave approaches shows the decrease in speed of the wave. This is due to the shallower sea bed near the beach Source//http:www.nasaimages.org

Wave bends towards normal
large wavelength Understanding refraction water glass Wave bends towards normal short wavelength Wave slows down when entering denser medium, experiencing higher resistance

Conclusion Wave motion is the result of vibrations.
There are two types of waves: transverse and longitudinal. Wave travels as the particles vibrate about their fixed positions. Relationship v = f x  us to determine the speed of wave. The wavefront tells us direction of travel and their distance between tells us the wavelength. Changes in wavefront gives us an indication of changes in wave medium.