TWO-SOURCE+INTERFERENCE+OF+WAVES

Back to IB PHYSICS > EM WAVES OPTION =TWO-SOURCE INTERFERENCE OF WAVES= State the conditions necessary to observe interference between two sources. [|PHET WAVE INTERFERENCE SIMULATION] investigate the conditions for interference at the PHET website. Explain, by means of the principle of superposition, the interference pattern produced by waves from two coherent point sources.
 * WAVES AND SOURCES || OPTICAL INSTRUMENTS || TWO-SOURCE INTERFERENCE || DIFFRACTION GRATING || X-RAYS || THIN-FILM INTERFERENCE ||

SUPERPOSITION: When two waves pass the same point at the same time, their displacements are added together to calculate the resultant displacement. COHERENT: Sources of waves with the same frequency, similar amplitude and constant phase difference are coherent. CONSTRUCTIVE INTERFERENCE: When two coherent sources, which are in phase, superpose, they add to give a wave of double amplitude. Also called Reinforcement. DESTRUCTIVE INTERFERENCE: When two coherent sources, which are out of phase, superpose, they add to give a wave of zero amplitude. Also called Cancellation.

The effect may be illustrated using water waves and sound waves in addition to EM waves.



Outline a double-slit experiment for light and draw the intensity distribution of the observed fringe pattern.

DOUBLE SLIT EXPERIMENT: Light from two point sources interfere and cause a pattern of fringes caused by constructive and destructive superposition. PATH DIFFERENCE: The distance, measured in wavelengths, between the paths taken by 2 waves.



This should be restricted to the situation where the slit width is small compared to the slit separation so that diffraction effects of a single slit on the pattern are not considered.

Solve problems involving two-source interference.