WAVES

WAVES

1. WAVES ARE OSCILLATIONS OF PARTICLES OR ELECTROMAGNETIC FIELDS.

   • OSCILLATIONS TRANSFER ENERGY IN THE DIRECTION THE WAVE TRAVELS.
     • MECHANICAL WAVES ARE THOSE THAT ARE TRANSMITTED BY THE OSCILLATION OF PARTICLES IN A MEDIUM.
       • ELECTROMAGNETIC WAVES INVOLVE OSCILLATIONS OF ELECTROMAGNETIC FIELDS. THEY DO NOT INVOLVE PARTICLES.
         • IN TRANSVERSE WAVES PARTICLES/ EM FIELDS OSCILLATE AT RIGHT ANGLES TO THE DIRECTION OF THE WAVES MOTION
           • IN LONGITUDINAL WAVES PARTICLES OSCILLATE IN THE SAME DIRECTION OF THE WAVES MOTION.

2. WAVE PARAMETERS

   • ARE MEASUREMENTS MADE OF IMPORTANT WAVE FEATURES
     • AMPLITUDE IS THE MAXIMUM DISTURBANCE OF PARTICLES OR A FIELD FROM REST POSITION.
       • WAVELENGTH IS THE DISTANCE BETWEEN SUCCESSIVE CRESTS OR TROUGHS.
         • PERIOD IS THE TIME TAKEN FOR A WAVE TO TRAVEL ON WAVELENGTH.
           • FREQUENCY S THE NUMBER OF COMPLETE WAVES PASSING A POINT EACH SECOND.
             • VELOCITY IS THE RATE AT WHICH THE WAVE MOVES THROUGH THE MEDIUM OR VACUUM
               • FREQUENCY IS RELATED TO PERIOD BY F=1/T
                 • VELOCITY IS RELATED TO WAVELENGTH BY V=FL

3. WAVE FRONTS

   • WAVE FRONTS ARE TRAVELLING CRESTS OF WAVE.
     • CIRCULAR WAVE FRONTS ARE PRODUCED BY THE OSCILLATION OF A POINT SOURCE.
       • PLANE WAVE FRONTS CAN BE PRODUCED BY THE OSCILLATION OF MANY POINT SOURCES.
         • WAVE FRONTS OCCUR AT RIGHT ANGLES TO THE WAVES DIRECTION OF MOTION.
           • THE DIRECTION OF MOTION IS INDICATED BY LINES CALLED RAYS.

4. REFLECTION OF PULSES

   • A REFLECTED PULSE FROM A FREE END IS THE SAME WAY UP AS AN INCIDENT PULSE.
     • A REFLECTED PULSE FROM A FIXED END IS INVERTED RELATIVE TO INCIDENT PULSE.
       • PULSE LENGTH AND SPEED OF REFLECTED PULSES ARE THE SAME AS THE INCIDENT PULSE.
         • AMPLITUDE= SMALLER B/C SOME ENERGY IS LOST @ BOUNDARY.

5. WAVES AND BOUNDARIES

   • WHEN INCIDENT WAVE CROSSES BOUNDARY INTO DIFFERENT MEDIUM SPEED AND WAVE LENGTH WILL CHANGE.
     • THERE WILL ALSO BE A REFLECTED WAVE OFF THE BOUNDARY;.
       • E.G. TRANSMITTED WAVE SPEEDS UP IN DEEP WATER AND HAS A LONGER WAVELENGTH. REFLECTED WAVE WILL BE IN PHASE WITH THE INCIDENT WAVE.

6. PULSES AND BOUNDARIES

   • WHEN INCIDENT PULSE CROSSES BOUNDARY INTO DIFFERENT MEDIUM IT WILL EXPERIENCE A CHANGE IN SPEED AND PULSE LENGTH.
     • THERE WILL BE A REFLECTED PULSE OFF THE BOUNDARY.
       • REFLECTED PULSE IS SAME WAY UP (LIGHT ROPE ACTS AS A FREE END.

7. REFLECTION OF WAVES

   • REFLECTION OF WAVES INVOLVES THE BOUNCING OF WAVES OFF BARRIERS.
     • THE INCIDENT RAY GIVES THE DIRECTION OF MOTION.
       • THE REFLECTED RAY GIVES THE DIRECTION OF MOTION.
         • NORMAL IS PERPENDICULAR TO THE BARRIER THE RAY STRIKES IT AT RIGHT ANGLES.
           • LAW OF REFLECTION = THETA (R) = THETA (I)
             • WAVES SPEED, FREQUENCY AND WAVELENGTH ARE UNCHANGED.