E.g., d must be of the order of a millimetre or so and must be even smaller of the order of 0.1 or 0.2 mm. One must understand that both distances between two slits in Young’s double-slit experiment, d and a width of each slit have to be quite small, to be able to observe good interference and diffraction patterns, respectively. At this angle only, we get a maximum (not a null) for two different narrow slits which are separated by the distance of a. A diffraction pattern can be described as the superposition of the wave’s continuous family, which originates from each point on the single slit.įor the single slit of width, a, the first-ever interference pattern null takes place at an angle of λ/a. We calculate interference patterns while superposing two different waves that originate from the two different narrow slits. As we move to the successive maxima, the intensity starts to fall from the centre on both sides. On the other hand, the diffraction pattern is described as the central bright maximum, twice as broad as the maxima. The interference pattern is the one that consists of the number of equally spaced dark and bright bands.
Difference between diffraction and interference: As bandwidth is directly proportional to λ, the red bandwidth is wider than the violet bandwidth. The central maximum is white, but other bands are coloured. If the source is white light, the diffraction pattern is coloured. The central bright fringe has maximum intensity and the intensity of successive secondary maxima decreases rapidly. Diffraction pattern difference at the single slit because of the monochromatic white light:įor monochromatic light, the diffraction is of alternate bright and dark bands of unequal widths. The above conditions for diffraction maxima and minima are exactly the reverse of mathematical conditions for interference maxima and minima.
Hence, the diffraction pattern will be as described ahead:- Point C corresponds to the position of the central maxima. The total path difference between parallel rays will beĪ sin θ n = (2n + 1) λ/2, Therefore, they interfere constructively to give the maxima (bright fringe). Wavelets from a single wavefront reach the C centre onto the screen in the exact same phase. The width of the slit LN = a is of the wavelength of light order hence the diffraction takes place when the light beam reflects through a single slit. Diffraction of light at the single slit:Ĭonsider a parallel beam of light with the plane wavefront falling on the single slit LN. It becomes way more pronounced in case the aperture or the obstacle’s dimension is comparable to the light’s wavelength.Īccording to Fresnel, diffraction occurs on account of mutual interference of secondary waveless starting from portions of the wavefront which are not blocked by the obstacle or from portions of the wavefront which are allowed to pass through the aperture. Diffraction is the general characteristic exhibited by all types of waves.ĭiffraction of light can be described as the bending of lights in sharp corners along with spreading of or within the opaque obstacles’ geometrical shadow. Bending of light around the sharp corners, a spreading of light within the geometrical shadow of opaque obstacles is called diffraction of light.
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