The nature of waves Flashcards
What is the definition of a progressive wave?
A pattern of disturbances through a medium, carrying energy with it, involving the particles of the medium oscillating about their equilibrium position. It does not involve the transfer of matter.
What is the value of wave speed in any region of the EM spectrum in a vacuum?
3x10 8 ms-1
What are transverse waves?
The oscillations of the particles are at 90 degrees to the waves direction of travel.
What are longitudinal waves?
The oscillations of the particles are parallel to the waves direction of travel.
What is wavelength and its unit of measurement?
The minimum distance between two points on a wave oscillating in phase, measured in metres.
What is frequency and its unit of measurement?
The number of cycles of a wave that pass a given point in one second, measured in Hertz (s-1).
What is amplitude and its unit of measurement?
The distance from the middle of a wave to the crest measured in metres.
What is wave speed and its unit of measurement?
The distance travelled by the wave in one second, measured in ms-1.
How does a wave oscillate in phase?
Its oscillations will be multiples of 360.
How does a wave oscillate in antiphase?
Its oscillations will be 180 degrees out of phase.
What is wave phase?
The relationship between the pattern of vibration of two points of a wave.
Give an example of a transverse wave
An electromagnetic wave
Give an example of a longitudinal wave
A sound wave
What is the wave source?
An oscillating object in contact with the medium.
Describe the oscillations in a polarised transverse wave
The oscillations are in just one direction at a right angle to the waves direction of travel.
Describe the oscillations in an unpolarised transverse wave
The direction of oscillation keeps changing randomly, but is always at right angles to the direction of travel.
How are two waves in phase?
The waves are at the same point in their cycle at the same time.
When are two waves in anti phase?
The waves are out of phase by half a cycle, so have displacement in opposite directions.
What is the period of an oscillation?
The time taken for one complete cycle (T=1/f).
What is a wavefront?
The surface on which all oscillations are in phase.
Give examples of unpolarised light emitters
The sun and domestic light bulb.
How should the two polaroid sheets be orientated in order to view light?
Parallel to each other.
How should the two polaroid sheets be orientated in order to view no light?
At right angles to each other, polaroids are crossed.
