![]() Moreover, this phenomenon causes light from a coherent source to interfere with itself, which in results in creating a distinctive pattern on the screen called the diffraction pattern. Question 2: What is meant by single-slit diffraction?Īnswer 2: In the single-slit diffraction, observance can be made of the phenomenon of bending of light or diffraction. (b) The drawing shows the bright central maximum and dimmer and thinner maxima. The central maximum is six times higher than shown. Monochromatic light passing through a single slit has a central maximum and many smaller and dimmer maxima on either side. Moreover, the central maxima is obtainable at point 0 on the screen. Discuss the single slit diffraction pattern. Furthermore, central maxima is surrounded by dark and bright lines known as the secondary minima and maxima. Question 1: What is meant by diffraction maxima and minima?Īnswer 1: The diffraction pattern involves a central bright fringe, also known as the central maxima. ⇒ Angular width of central maximum = 2θ = 2λa FAQs For Single Slit Diffraction Well, the width of the central maximum is simply twice this value Now, one may ask how to find width of central maximum. When diffraction of light occurs as it passes through a slit, the angle to the minima (dark spots) in the diffraction pattern is given by d sin n. The position of the minima expressed by y (whose measurement takes place from the centre of the screen) is: Furthermore, it simply refers to the distance between the first order minima from the centre of the screen existing on both sides of the centre. The maxima lies between the minima and the width of the central maximum. Although this effect is small for large apertures. Similarly, for the nth fringe, division of the slit can take place into 2n parts and this condition can be used as: 6.2 Interference and diffraction Huygen ’s Principle Single slit diffraction Circular diffraction The diffraction limit Diffraction effects of apertures When light is passed though an aperture the light beam is smeared out. As such, one can obtain a dark fringe.įor the next fringe, division of the slit can take place into 4 equal parts of a/4 and the same logic can be applied. Therefore, at θ = sin − 1λa, there would be destructive interference because any ray emanating from a point has a counterpart that produces destructive interference. Furthermore, the path difference must be out of phase by λ2, with λ being the wavelength.įor a ray emanating from any point in the slit, there exists another ray at a distance a/2 from which destructive interference can take place. Moreover, one can consider any arbitrary pair of rays at a distance a/2.įor a dark fringe, the path difference must produce destructive interference. ![]() Furthermore, it is possible to consider any number of ray pairings that start from a distance a/2 from one another. The path difference exhibited by the top two rays is:Īn important point to remember is that this calculation is valid only if D is very large. Furthermore, consider a pair of rays whose emanation takes place from distances a/2 from each other. Also, the division of the slit can take place into zones of equal widths a/2. In order to describe the pattern, one must first look at the condition for dark fringes. Now, one can identify the angular position of any point on the screen by ϑ whose measurement takes place from the slit centre which divides the slit by a/2 lengths. x`D is the separation between slit and source. ![]() With the slit being completely open, however, the space between the slits (\(d\)) goes to zero, and the number of slits (\(n\)) goes to infinity.Single Slit Diffraction Formula of Single Slit DiffractionĬonsider that the slit width a << D. One way to think of this is to go back to the diffraction grating case, expressed in Equation 3.3.2. To compute the intensity of the interference pattern for a single slit, we treat every point in the slit as a source of an individual Huygens wavelet, and sum the contributions of all the waves coming out at an arbitrary angle. In a diffraction pattern due to a single slit of width a, the first minimum is observed at an angle 30o when light of wavelength 5000A is incident on the. Significantly more math is required to deal with the intensity of the bright fringes. The bright fringes only approximately follow the same spacing pattern, not exactly located halfway between the dark fringes, but using the pairwise approach doesn't tell us much about the intensity of those bright regions, for the same reason it didn't for the central bright fringe – constructive pairs will not be in phase with other constructive pairs.
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