Zusammenfassung der Ressource
Physics
'AS' & 'A'
Level:
Waves
- 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.
- 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
- 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
- INTENSITY
- INTENSITY = POWER / AREA
- ALTERNATIVELY
- INTENSITY ∝ AMPLITUDE(Square)
- INTENSITY = (Constant).AMPLITUDE(Square)
- INTENSITY = 2.π(Square).f(Square).ƿ.v.A(Square)
- 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