4.2 What Is A Wave? Flashcards
What is a wave?
Propagation of a disturbance through a medium.
What happens as a wave travels through the medium?
Molecules of the medium are displaced from equilibrium positions, made to oscillate about these positions in simple harmonic motion.
What can a wave transfer?
Energy and momentum.
What are some examples of mechanical waves?
Water waves, sound, earthquake waves.
What medium do mechanical waves travel through?
Require a physical medium, cannot propagate in vacuum.
What is the wave speed determined by for mechanical waves?
Determined by the properties of the medium.
What is the disturbance of particles in mechanical waves?
Change of a property of the medium from its equilibrium value - when there is no waves.
What are some example of electromagnetic waves?
Light, radio waves, X rays, infrared radiation, ultraviolet radiation.
What medium do electromagnetic waves travel through?
Can propagate in a vacuum as well as various physical media.
What is the wave speed determined by for electromagnetic waves?
In vacuum all waves travel at 3x10^8 ms^-1
What is the disturbance of particles in electromagnetic waves?
The oscillating values of electric and magnetic fields.
What is displacement?
Vector to the position of a point in a medium from the equilibrium position of the point.
What is amplitude?
Maximum displacement.
What is a crest?
Maximum positive displacement.
What is a trough?
Maximum negative displacement.
What is wavelength?
Length of a full wave. May be found from a displacement versus distance graph.
What is frequency?
Number of full waves produced by a source in 1 second - in Hz. Frequency is inverse of period f = 1/T
What is period?
Time taken fro one full wave to pass by. May be found from a displacement versus time graph. Period is inverse of frequency T = 1/f
What is wave speed?
Speed at which a crest moves past an observer at rest in the medium. v = f x lambda
What is intensity?
Power transferred per unit area by a wave. Proportional to the square of the amplitude. For a point source emitting uniformly in all direction, intensity a distance d from point source has intensity proportional to 1/d^2.
What is a transverse wave?
Displacement of medium is perpendicular to direction of wave movement or energy transfer.
What is a longitudinal wave?
Displacement of medium is parallel to direction of wave momentum or energy transfer.
What is a ray?
Lines indicating the direction of energy transfer of a wave.
What is a wavefront?
Surface at right angles to rays. All points on a wavefront have the same phase.
