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INTERFERENCE OF LIGHT
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DEFINITION
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| When two light waves from different coherent sources meet together, then the distribution of energy due to one wave is disturbed by the other. This modification in the distribution of light energy due to super- position of two light waves is called "Interference of light". | |||
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CONDITIONS
FOR INTERFERENCE
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The two sources of light should emit continuous waves of same wavelength
and same time period i.e. the source
should have phase coherence. The two
sources of light should be very close to each other.The waves
emitted by two sources should either have zero phase difference or no phase
difference. |
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COHERENT
SOURCES
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| Those sources of light which emit light waves continuously of same wavelength, and time period, frequency and amplitude and have zero phase difference or constant phase difference are coherent sources. | |||
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TYPES
OF INTERFERENCE
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......There
are two types of interference. Constructive
interference. Destructive
interference. |
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CONSTRUCTIVE
INTERFERENCE
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| When two light waves superpose with each other in such away that the crest of one wave falls on the crest of the second wave, and trough of one wave falls on the trough of the second wave, then the resultant wave has larger amplitude and it is called constructive interference. | |||
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CONDITIONS
FOR CONSTRUCTIVE INTERFERENCE
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| For
constructive interference, path difference between two waves is ml
i.e. path difference = ml or path difference = 0, l, 2l, 3l, 4l, ….. where m = order = 0, +_1, +_2, +_3,….. |
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EFFECTS
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In constructive interference, two waves of light reinforce each other. In constructive
interference, a bright fringe is obtained on the screen. |
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DESTRUCTIVE
INTERFERENCE
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| When two light waves superpose with each other in such away that the crest of one wave coincides the trough of the second wave, then the amplitude of resultant wave becomes zero and it is called destructive interference. | |||
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CONDITIONS
FOR
DESTRUCTIVE INTERFERENCE |
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If the path difference between two light waves is (m+1/2)l
, then the interference between them will be destructive. Path difference = (m+1/2)l i.e. path difference = 1/2l, 3/2l, 5/2l , …. where m = order = 0, +_1, +_2, +_3,….. |
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EFFECTS
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In destructive interference, two waves cancel the effects of each other. Due to
destructive interference a dark fringe is obtained on the screen. |
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