MUS

MUS

1. Types of waves

   • Transverse - the waves act perpendicular to the direction of travel. E.g. light waves
   • Longitudinal- the waves act parallel to the direction of motion. E.g. sound waves
     • Wavefront- a line representing a series of equivalent points on the waves (e.g. all the compressions
     • Regions of compressions and rarefractions

2. Features of waves

   • Amplitude- the maximum displacement from the equilibrium position
   • Wavelength- the shortest distance between two adjacent points that are in phase (peak to peak)
   • Frequency- the number of complete oscillations per second or the number of waves passing a point in one second
   • Period (T)- the time taken for one complete oscillations
   • Speed (v)- v=fλ

3. Superposition

   • In phase- if the peaks and troughs of two waves occur at the same time
     • Causes constructive interference
   • In antiphase- the peak of one wave occurs at the same time as the trough of another
     • Causes destructive interference
   • Def: if two or more waves arrive at the same place at the same time
   • Interference
     • Coherent- two sets of waves with the same frequency and a constant phase difference
     • Interference patterns- consist of alternate maxima and minima
       • If both waves are from same source, difference in path length determines phase difference at detector
         • Path difference = whole number = constructive interference
         • Path difference = odd no. of half wavelengths = destructive interference
   • Standing waves
     • Two waves travelling in opposite directions or meet by reflection
       • Superposition occurs
         • Producing nodes and antinodes
     • On a string - nodes at each end
     • Sound through a tube - closed end has nodes and open end has antinodes

4. The EM spectrum

   • Radiowaves have a longer wavelength than Gamma rays
   • Radiowaves
     • Wavelength is about 1m
     • Used for TV and radio transmissions
     • Does not diffract so requires line-of-sight receiver
   • Microwaves
     • Used for mobile phone links
   • Infrared
     • Used by some alarm systems
   • Visible light
   • Ultraviolet
     • Can cause fluorescence
     • UV detected from stars and galaxies
   • Xrays
     • Penetrating
     • Used to see in suitcases at airports
   • Gamma rays
     • Used in hospitals to sterilise equipments