![]() ![]() Let's begin by examining what happens to regular, non-coherent white light as it passes through an aperture (that's just a technical term for for a hole, or gap). In your own words: explain the difference between coherent and incoherent sources? Do some research and find some examples of coherent and incoherent wave sources (they need not be light waves - sound sources or other mechanical waves can also be coherent or incoherent.) The figure at left shows two sources one coherent, the other incoherent. If a source of waves is coherent, then we can predict when there will be constructive and destructive interference. In an incandescent bulb, the light waves are created due to more random processes, so the light waves emitted start with different phases and the phase relation between different waves will not be constant as time evolves. ![]() In a laser (which is a coherent source) all the waves that are emitted start with the same phase. Incoherent Wave sourcesĭefinition: Two sources are considered coherent if they emit waves that maintain a constant phase relation.Įffectively, this means that the waves do not shift relative to one another as time passes. This lab will explore the physics behind this idea. An easy way to control the relation between two waves is by having them travel different distances before combining, thus creating a path-length difference and allowing for interference effects. If one is at a maximum, and the other a minimum, then the sum of the two waves at that point will be zero. If they are both at the minimum amplitude, $-A$, then the result will be $-2A$. If both waves are at their maximum amplitude $A$, then the result is $2A$. One of the consequences of the wave nature of light is that the principle of superposition applies: two waves can be combined by simply adding their amplitudes. If not, check again, then talk to your lab instructor. Please make sure your station has all of the following items. All lasers should be handled with care, and you should never look directly into the beam. You will use this property to calculate properties of light. This lab will demonstrate the wave nature of light. Lab Instructor = please log in Introduction Interference of Light ![]()
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