Wave can be added together either
constructively or destructively. The result of adding two
waves of the same frequency depends on the value of the
phase of the wave at the point in which the waves are
added.
Electromagnetic waves are subject to interference. For
two sources of electromagnetic waves to interfere.
The sources must have the same frequency and polarization.
The sources must be coherent.
The superposition principle must apply.
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Young's Double Slit Interference
In the double slit experiment, a single source is split in two,
to generate two coherent sources.
When the light from the two sources is projected on a screen,
an interference pattern is observed.
To explain the
origin of the interference pattern, consider the distance
traveled from the two sources. At the center of the
screen the waves from the two sources are in phase. As we
move away from the center, the path traveled by the light
from one source is larger than that traveled by the light
from the other source. When the difference in path is
equal to half a wavelength, destructive interference
occurs. Instead, when the difference in pathlength is
equal to a wavelength, constructive interference occurs.
This is a classic
example of interference effects in light waves. Two light
rays pass through two slits, separated by a distance d
and strike a screen a distance, L, from the slits. You
can change this parameters (drag scrollbars to do it) and
you see the result of interference on the screen.
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