Patterns of problems
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Wave Optics

- Get the best out of this chapter by practicing the kind of problems asked in various Exams
1
Pattern: Superposition of wave
Description: When two light wave reaches simultaneously at a point, The resultant disturbance of medium particles can be explained by the superposition principle. Amplitude of resultant disturbance can be calculated by vector addition of amplitude of individual disturbances. Intensity is directly proportional to square of amplitude () so we can use the equation where represent phase difference between waves. Phase difference can also be found from given equation of wave.
Question may ask: Amplitude of resultant disturbance, Phase difference between waves, Intensity of resultant waves ( same or different intensity)
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2
Pattern: Interference of light
Description:In interference, two monochromatic light waves are superimposed. If sources are coherent then definite patterns of intensity obtain on-screen but when sources are non-coherent then constant intensity obtain on the screen (). Maximum intensity on screen obtain when path difference between incident wave and for minimum intensity, path difference would be . Intensity and phase difference is related with the equation where represent maximum intensity of individual waves. For central maxima, Path difference should be equal to zero and distance between two consecutive maximama/ minima is called firnge width ().
Question may ask: Location of central maxima, Fringe width, Angular fringe width, Location of order maxima or minima, Maximum number of maxima and minima obtained on-screen, Based on relation among Path difference, Phase difference and intensity.
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3
Pattern: Polarisation of light
Description: when unpolarised light passed through polaroids then it gets polarised. It can also be polarised by refraction and reflection. During polarization, intensity of light decreases. When polarised light passing through another polaroid which axis make angle with axis of the previous polaroid then intensity obtain on-screen after final pass would be . Also when unpolarised light incident on refracting surface at brewster's angle then reflected rays get fully polarised whereas refracted rays get partially polarised.
Question may ask: Intensity of polarised wave, Angle of polarization
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