P1.5 Waves

P1.5 Waves

1. Properties

   • Waves transfer energy
   • Either transverse or longitudinal
     • EM waves are transverse
     • Sound waves are longitudinal
     • Show areas of compression and rarefraction
   • Can be...
     • Reflected
     • Refracted
       • Change of direction
         • Not refracted if travelling along the normal
     • Diffracted
   • All waves obey the equation - wave speed = frequency x wavelength

2. Electromagnetic Waves

   • Forms a continuous spectrum
   • Travel at the same speed
     • Speed of light
     • Through a vacuum
   • In order of longest wavelength to shortest
     • Radio waves
       • Micro Waves
         • Infrared
           • Visible light
             • Ultra Violet
               • X-Ray
                 • Gamma ray
                   • Sterilising, Treat and detect cancer
                 • Observing internal structure- airport security, medical scans
               • Security marking
             • Photography, Vision
           • Optical fibres- Remote controls, Thermal Images
         • Satellite- TV, Phones
       • Communicating- Radio
     • Wavelengths from 10 to -15 metres to 10 to 4 metres

3. Reflection

   • Normal
     • Construction line perpendicular to the reflecting surface at the point of incidence
   • Angle of incidence = angle of reflection
   • Image produced in a plane mirror
     • Virtual

4. Sound

   • Longitudinal
   • Cause vibrations
     • Detected as sound
   • Pitch
     • Determined by frequency
     • Loudness
       • Determined by amplitude
   • Echoes are reflections of sound

5. Red-shift

   • Doppler effect
     • Wave source is moving
       • Could be light, sound or microwaves
         • When source moves away
           • Wavelength increases
             • Frequency decreases
           • When source moves towards
             • Wavelength decreases
               • Frequency increases
   • Further the galaxies
     • Faster they are moving
       • Bigger the increase in wavelength
         • Appear red coloured
           • Red-shift
             • Provides evidence that the universe is expanding and supports the 'Big Bang' theory
               • Cosmic Background radiation explained by Big Bang
                 • Form of electromagnetic radiation filling the universe, comes from radiation present shortly after the beginning of the universe