Topic 11 – Wave Phenomena

11.1 – Standing/ Stationary Waves

Standing Waves

• Formation of standing wavesStanding waves are formed when two identical waves met each other travel in opposite directions.

Wiki – Waves on a string

Standing Waves

• The result of this is a wave where the peaks simply move up and down but DO NOT PROGRESS.

Standing vs Progressive WavesStanding Progressive

Amplitude All points on the wave have different amplitudes. The maximum being 2A (at the antinodes) and 0 (at the nodes)

All points on the wave, have the same amplitude

Frequency Oscillate with the same frequency

Oscillate with the same frequency

Wavelength Twice the distance for one node to the next node

Shortest distance between two points that are in phase

Phase All points between one node and the next node are in phase

All points along a wavelength have different phases

Energy Energy is not transmitted by the wave but it does have an energy associated with it.

Energy is transmitted by the wave.

Formation of Standing Waves

Formation of Waves in Closed Pipes

Formation of waves in open pipes

11.2 Doppler Effect

• The change in pitch of a sound wave due to a change in frequency of the wave is called the Doppler Effect.

• It is caused by the relative motion of the SOURCE and the DETECTOR

Moving Source

Moving Observer

Doppler Effect and EM radiation

• The EM spectrum travels at c through a vacuum but if the velocity of the observed EM radiation in a lot smaller than c then we can use the following equation to calculate the change in frequency

For v << c

Doppler Effect Equations

Using the Doppler Effect!

• 11.2.6 – Outline an example in which the Doppler Effect is used to measure speed.

11.3 Diffraction

• More in depth look at diffraction

• Huygens’ Principle

• http://www.acoustics.salford.ac.uk/feschools/waves/diffract3.php

Diffraction from a single slit

• What is the diffraction pattern shown on a screen when a wave is diffracted around a single slit?

Explaining the diffraction pattern

Explaining the diffraction pattern

Explaining the diffraction pattern

Explaining the diffraction pattern

Explaining the diffraction pattern

11.4 Resolution

• If two sources sources of light are very close in angle to each other they can sometimes be seen as one light source.

• If we can detect that there are two light sources then we say the light sources are resolved

• The ability to do this depends on the RAYLEIGH CRITERION

Rayleigh Criterion

Rayleigh Criterion

• If the sources are to be just resolved, then the minimum of one diffraction pattern is located on top of the maximum of the other diffraction pattern.

• For a SLIT – the minima was located at• For a CIRCULAR APERTURE -

Importance of Resolution

Research the importance of resolution in the development of the following technologies

• CDs

• DVDs

• Electron Microscope

• Radio Telescopes

11.5 Polarisation