Physics 'AS' & 'A' Level: Waves

Physics 'AS' & 'A' Level: Waves

1. CAN BE DESCRIBED BY TERMS

   • - Amplitude (A)
     • The maximum displacement of any point on the wave from its undisturbed position is called the amplitude A.
   • - Wavelength (λ), λ= v/f
     • The distance from any point on a wave to the next exactly similar point (e.g. crest to crest) is called the wavelength λ
   • - Frequency (f), f = v/λ
     • The number of oscillations per unit time of a point in a wave is called its frequency f.
   • - Wave Speed (v), v = f λ
     • Speed with which energy is transmitted by a wave
   • - Period (T), T = 1/f
     • The time taken for one complete oscillation of a point in a wave is called the period T.

2. CAN BE REPRESENTED BY GRAPH

   • DISPLACEMENT-DISTANCE GRAPH
     • SHOWS HOW DISPLACEMENT VARIES WITH DISTANCE FOR ALL PARTICLES IN A WAVE AT ONE INSTANT
   • DISPLACEMENT-TIME GRAPH
     • SHOWS HOW DISPLACEMENT VARIES WITH TIME FOR ONE PARTICLE IN A WAVE

3. ALL WAVES ARE CAUSED BY SOME TYPE OF VIBRATION

   • IN LONGITUDINAL WAVES, THE PARTICLES OF THE MEDIUM VIBRATE PARALLEL TO THE DIRECTION OF THE WAVE VELOCITY. E.g: SOUND WAVE
     • ULTRASOUND IS ANY SOUND WAVE THAT HAS A FREQUENCY ABOVE 20 kHz (20 000 Hz)
       • Ultrasound transducers use the piezo-electric effect (of a crystal) to generate and detect ultrasound waves
   • IN TRANSVERSE WAVES, THE PARTICLES OF THE MEDIUM VIBRATE AT RIGHT ANGLES TO THE DIRECTION OF THE WAVE VELOCITY. E.g: Water & Electromagnetic Waves
     • CAN BE POLARISED
       • POLARISATION – CONFINE THE OSCILLATIONS OF THE ELECTRIC VECTOR OF LIGHT WAVES TO ONE DIRECTION.
     • ELECTROMAGNETIC WAVES

4. INTENSITY

   • INTENSITY = POWER / AREA
     • ALTERNATIVELY
       • INTENSITY ∝ AMPLITUDE(Square)
       • INTENSITY = (Constant).AMPLITUDE(Square)
       • INTENSITY = 2.π(Square).f(Square).ƿ.v.A(Square)

5. DOPPLER EFFECT

   • (OR THE DOPPLER SHIFT) IS THE CHANGE IN FREQUENCY OF A WAVE IN RELATION TO AN OBSERVER WHO IS MOVING RELATIVE TO THE WAVE SOURCE (OR VICE VERSA).
     • SOURCE IS APPROACHING THE OBSERVER
       • f(Observer) = [ f(source) v ] / [v - v(source) ]
     • SOURCE IS MOVING AWAY FROM THE OBSERVER
       • f(Observer) = [ f(source) v ] / [v + v(source) ]
       • AS DISTANCE AWAY FROM THE SOURCE INCREASE, THE INTENSITY DECREASES BECAUSE:
         • (1) THE WAVE MAY SPREAD OUT & (2) THE WAVE MAY BE ABSORBED OR SCATTERED

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