Waves P1.5

Waves P1.5

1. Nature of waves

   • We use waves to transfer energy and information
   • Transverse waves vibrate perpendicular to the direction of energy transfer. e.g all electromagnetic waves
   • Longitudinal waves vibrate parallel to the direction of energy transfer. e,g sound wave
   • Mechanical waves, need a medium to travel through, can be transverse or longitudinal

2. Measuring waves

   • Amplitude is the height of the wave crest or depth of wave trough from position at rest
   • Frequency is the number of wave crests passing a point in one second
   • Wavelength is the distance from one wave crest to the next wave crest - same with trough
   • v = f x λ

3. Wave properties: reflection

   • Normal at a point on a mirror line is a line drawn perpendicular to the mirror
   • Angles are always measured between light ray and normal
   • Law of reflection states angle of incidence = angle of reflection

4. Wave properties: refraction

   • Refraction of light is the change of direction of a light ray when it crosses a boundary between 2 transparent substances
   • If speed is reduced refraction is toward the normal e.g air to glass. angle of refraction is less then incidence
   • If speed is increased refraction is away from the normal e.g glass to air angle of refraction is greater then incidence

5. Wave properties: diffraction

   • Spreading out of waves when they pass through a gap or round the edge of an obstacle
   • The narrower a gap the greater the diffraction
   • If radio waves don't diffract enough when they go over hills, reception would be poor

6. Sound

   • Frequency range of the normal human ear is from 20 Hz to 20 kHz
   • Sound waves are longitudinal
   • Sound waves need a medium in which to travel. cannot travel through a vacuum e.g space
   • Reflections of sounds are called echo

7. Musical sound

   • Pitch of a note increases if frequency of sound wave increases
   • Loudness of a note depends on amplitude of the sound waves
   • Vibrations created in an instrument when it is played produce sound waves