![]() Figure 4.2.2 shows a single-slit diffraction pattern. Textbook content produced by OpenStax is licensed under a Creative Commons Attribution License. Light passing through a single slit forms a diffraction pattern somewhat different from those formed by double slits or diffraction gratings, which we discussed in the chapter on interference. This means the light reaching the screen could have come from anywhere within the slit. Use the information below to generate a citation. When light passes through a narrow gap it will diffract (spread out). Then you must include on every digital page view the following attribution: If you are redistributing all or part of this book in a digital format, Then you must include on every physical page the following attribution: If you are redistributing all or part of this book in a print format, ![]() We get second secondary maxiumum of lower intensity.Want to cite, share, or modify this book? This book uses the Similarly if the path difference at that point is given by However, the secondary waves from the third part remain unused and therefore, they will reinforce each other and produce first secondary maximum. This will give rise to destructive interference. Here, we can consider the wavefront to be divided into three equal parts, so that the path difference between secondary waves from corresponding points in the 1st two parts will be λ/2. Let's assume that the slit is constant width and very tall compared with that width, so that we can consider the system as two-dimensional. The sketch shows the view from above a single slit. By passing light through a single slit, an interference pattern can be observed similar to that of the double slit experiment. Then P 1 will be position of first secondary maximum. A laser illuminates a single slit and the resultant patten is projected on a distant screen. If any other P' is such that the path difference at that point is given by An adjustable slit is placed on the table of a spectroscope and a monochromatic light source is viewed through it using the spectroscope telescope (see Figure 1. Such a point on the screen will be the position of the second secondary minimum. Such a point on the screen will be the position of the first secondary minimum. Then, the above equation gives the following relation: Thus, at P, destructive interference will take place.įrom the right-angled ΔANB given in part (ii), Also, for every point in the upper half AC, their is a corresponding point in the lower half CB for which the path difference between secondary waves reaching P is λ/2. If the path difference between secondary waves from A and B is λ, then the path difference between secondary waves from A and C will be λ/2, and also the path difference between secondary waves from B and C will again be λ/2. This is because the whole wavefront can be considered to be divided into two equal halves CA and CB. What is the width of the slit (mm) if the width of the central maximum is 2.37 cm 6.311047 m Submit Answer Incorrect. The pattern is viewed on a screen placed one meter from the slit. If this path difference is λ, then P will be a point of minimum intensity. (c24p28) A single-slit diffraction pattern is formed when light of A 617.0 nm is passed through a narrow slit. The intensity at P will depend on the path difference between the secondary waves emitted from the corresponding points of the wavefront. The wavelets from points A and B will have a path difference equal to BN. The secondary waves travelling in the direction making an angle θ with CO, will reach a point P on the screen. ![]() ![]() These secondary waves reinforce each other, resulting in maximum intensity at point O. The secondary waves, from points equidistant from the centre C of the slit lying in the portion CA and CB of the wavefront travel the same distance in reaching O, and hence the path difference between them is zero. According to Huygens principle, each point on the unblocked portion of plane wave front AB sends out secondary wavelets in all directions. (ii) Diffraction of light due to a narrow single slitĬonsider a set of parallel rays from a lens L 1 falling on a slit, form a plane wavefront. (b) Wavelength of the light used should be comparable to the size of the obstacle. Mount a laser on the optics bench along with the slide with variable width thin slits to show diffraction of light as shown in the picture at far left. (a) Source of light should be monochromatic. ![]()
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