COMBINING WAVES Flashcards
Define Phase Difference.
Difference in angle of the vectors corresponding to two points on the same wave.
State the criteria for stationary waves to be created.
Two waves travelling past each other in opposite directions.
With same frequency/wavelength.
Similar amplitudes.
Describe how a stationary wave is formed on a string.
Produced when reflected wave and incident wave overlap. From principle of superposition it is then produced.
Define Superstition.
Refers to the vector addition of displacements of two waves overlapping.
Describe how stationary wave formed using microwave transmitter.
Microwave transmitter placed away from metal plate.
The aerial connected to the speaker is moved away from the transmitter.
As this happens series of maxima and minima signals detected.
Microwaves reflected off metal plate.
Maxima and minima correspond to antinodes and nodes.
Distance between two adjacent nodes or antinodes is lambda/2.
Define coherent sources.
Source (or sources) with a constant phase difference and same wavelength.
Define Path Difference.
Extra distance one wave has to travel to reach the same point as the other wave.
Define Constructive Interference.
Two waves adding together to produce larger amplitude.
Define Destructive Interference.
Two waves adding together to produce smaller amplitudes.
Describe Interference between two speakers.
Two speakers are coherent.
When path difference between waves is zero or an even number the two waves arrive in phase.
From Principle of Superposition produces constructive interference corresponding to LOUD region.
When path difference between waves from each speaker half wavelength waves arrive in anti-phase.
Produces destructive interference corresponding to QUIET region.
Define Diffraction.
Spreading out of a wave when it passes through a narrow aperture.
Define Refraction.
A wave changes direction due to a change in speed.
Define Dispersion.
When (white) light spreads out into its component colours.
Describe Young’s Slits.
Coherent laser light passes through the two slits. They diffract and as the two waves overlap they produce interference effects. This is seen on the pattern on the screen having series of minima (dark spots) and maxima (light spots) being evenly spaced and parallel to eachother.
Explain what happens when white light passes through double slits.
All colours of white light have a path difference of zero to centre of pattern so all colours produce a bright fringe. All colours together look white.
Then either side we have a spectrum of light having blue closest to the central fringe as it has the Shortest wavelength.
