P:6 Part 2

P:6 Part 2

1. Reflection

   • when waves meet the boundary between two mediums, they can be reflected, refracted, absorbed or transmitted
   • ray diagrams are used to show what happens
   • when constructing a ray diagram:
     • rays must be drawn using a ruler
     • each straight section of ray should have a single arrow drawn to indicate the direction of movement
     • where the ray meets a boundary, a normal must be drawn at right-angles to the boundary
     • all relevant angles should be labelled
   • when waves are reflected at the surface, the angle of incidence is equal to the angle of reflection

2. Sound Waves

   • have a frequency, amplitude and wavelength
   • the amplitude reflects the loudness
   • frequency and wavelength reflect the pitch - higher frequency = higher pitch
   • normal range of human hearing is 20Hz to 20kHz
   • sound can travel through liquids, solids and gases
   • sound in any medium is due to the vibrations of the particles in that medium
   • in a solid, these oscillations can cause the entire solid to vibrate with the same frequency as the sound wave
   • the conversion of sound waves to vibrations only occurs over a limited range of frequencies. This range is dependent on the object
   • within the ear, sound waves cause the eardrum and other structure to vibrate and this is heard as sound
   • the limited range of conversion is what limits human hearing

3. Refraction

   • when a wave passes from one media to another it can be refracted and change direction. The direction of refraction depends on:
     • the angle the wave hits the boundary at
     • the material involved
   • for light rays, the way a material affects refraction is called its refractive index
   • when light travels:
     • from low to high refractive index, it bends toward the normal
     • from high to low refractive index, it bends away from the normal
   • due to the difference in wave speed in a material
   • when a light wave enters, at an angle, a medium in which it travels slower:
     • the first part of the wave to enter the medium slows down
     • the rest of the wave continues at the higher speed
     • this cause the change in direction, toward the normal

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