11 - Waves 1 Flashcards
What is a wave?
A physical phenomenon and that transfers energy through a medium without a transferring matter.
Waves travel or transfer energy through oscillations in a medium.
Either particles of a medium oscillate (mechanical wave)
OR electrostatic & magnetic fields in a medium vibrate (EM Waves)
What are the types of waves?
There are only two types of waves mechanical and EM
Transverse and longitudinal are modes of vibration - how vibrations happen with respect to direction of energy transfer
What is a transverse wave?
Waves in which the direction of oscillation is perpendicular to the direction of wave travel or energy transfer
Examples:
Waves on surface of water and electromagnetic waves
What is a longitudinal wave?
Wave in which direction of oscillation is parallel to the direction of wave travel (energy transfer).
Example:
Sound wave
Define displacement
The distance from the equilibrium position in a particular direction. Displacement is a vector, so it has a positive or negative value
Define amplitude
The maximum displacement from the equilibrium position (can be positive or negative)
Define wavelength
The minimum distance between two points oscillating in phase*. For example the distance from one pig to the next or from one compression to the next
- two adjacent vibrating particles/points with the same velocity at same displacement
DISTANCE BETWEEN 2 POINTS THAT ARE IN PHASE
Define period
Oscillations-the time taken for particle/point to complete one oscillation
Waves – time taken for one complete wavelength to pass a given point
Define phase difference
The difference between the displacement of particles along a wave (or on different waves)
Measured in degrees or radians
Each complete cycle or a difference of 1 wavelength representing 360° or 2 TT radians
Define frequency
Oscillations – number of complete oscillations per unit time. Hertz, Hz
Waves – the number of wavelengths passing a given point per time
Explain wave speed
The speed at which a wave travels through the medium is constant, and determined by properties of medium.
Thus, the higher the frequency of a given type of wave, the shorter its wavelength.
The speed is a fundamental property that changes when crossing between media, leading to change in wavelength (never frequency)
The wave equation
v = f x wavelength (aka lambda)
Speed of electromagnetic waves
3 x 10 ^8 m/s
Frequency and time period relationship
F = 1/T
Equation for speed of EM waves
c = f x wavelength (aka lambda)
Types of progressive waves
Transverse and longitudinal
How to use an oscilloscope to determine frequency?
A
Graphical representation of transverse & longitudinal waves
Transverse : wave with crests and troughs
Longitudinal : wave with compressions and rarefactions
What is the phase of a particle/ point ?
Fraction of a complete cycle/wave that a particle is at (at any given moment in time)
What is phase difference? And what types?
Difference in phase between 2 points along same wave or between 2 different waves at any given point in time.
What is phase difference measured in ?
Phase difference of 1 complete wave?
Radians, rad.
I complete wave = 2pi radians
General formula to calculate phase?
Fraction of wave completed x 2pi
How to calculate phase difference between 2 points on same wave ?
2 points, distance d apart, along wavelength (lambda):
Phase difference = (d/ lambda) x 2pi
How to calculate phase difference between 2 different waves, when they meet/ interact?
- at a given point in TIME, the difference between phases of each wave
Phase difference = (current phase in wave 1) - (current phase in wave 2)