^Diffraction spread From the above discussion it is clear that a parallel beam of light of wavelength λ on passing through an aperture of size d gets diffracted into a beam of angular width, If a screen is placed at distance D, this beam spreads over a linear width, If the diffraction spread y is […]
^Intensity of fringes Intensity of fringes at point P is Here I0 is the intensity of central maxima. For nth secondary maxima, From above points we have the following plot. Also using the relation of intensity we can say Maximum intensity is central maxima. Most of the light is diffracted between the two first order […]
^Position of maxima Also it is found that at P for nth maxima In a similar way the angular position of nth bright fringe is i.e. angular positions of 1st, 2nd, 3rd maxima are From above relation we can say that each secondary maxima occupies an angular width of , thus linear width of each […]
^Position of minima Path difference between the wavefronts reaching P from the end of the slits B & A is, x or p = BP – AP = AN Also p = d sinθ = A detailed mathematical analysis shows that at P for nth minima p = d sinθ = nl, n = ± […]
^Diffraction & Huygens’ theory Diffraction can be explained using Huygens’ theory. According to this theory all parts of the slit AB will become source of secondary wavelets, which all start in the same phase at that position. The wavefronts from any two corresponding points such as (1, 13), (2, 12), (3, 11) etc. from the […]
^Diffraction of light When a wave (light or sound) strikes an obstacle it doesn’t go straight, rather it bends round the obstacle. Also when a light wave passing from a narrow slit of width AB = d reaches screen placed at a distance D (>>d) from the slit, (Fig. A) then a bright spot on […]
^Young’s double slit experiment A common experiment to study interference of two light waves is YDSE. In this experiment overlapping of wave fronts of light waves coming from two slits S1 & S2 is studied by placing a screen at some distance from the slits. Let slits are separated by a distance ‘d’ & screen […]
^Interference with independent light sources Two independent light sources can’t produce a sustained interference, rather they produce uniform illumination on the screen, as the phase of the light emitted by them very rapidly (108 times in every one second) in other words two independent light sources are incoherent.
^Coherent sources If the positions of constructive & destructive interference remain fixed (or sustained) with time if the phase difference between the overlapping waves remains constant with time, such waves are called coherent & sources producing such waves are called coherent. Coherence is essential condition to observe interference pattern. Coherence: Φ ∝ time0 or constant
^Interference of waves Let two waves of amplitudes a1 & a2 having a phase difference ΔΦ (or simply Φ) superpose (overlap) at a point P. Let R be the amplitude of the resultant wave, from principle of superposition (POS) R is As for any wave intensity is proportional to square of its amplitude, i.e. Let […]
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