There is more about how the angle $\alpha$ is related to the wavelength of the light, the slit width and the slit separation in this answer and in many textbooks and websites. That is, their bright fringes are narrower and brighter while their dark regions are darker. What makes them particularly useful is the fact that they form a sharper pattern than double slits do. A single slit of finite width produces a diffraction pattern. Diffraction gratings are commonly used for spectroscopic dispersion and analysis of light. It is a graph of relative intensity (y-axis) against position (x-axis). The first term is the diffraction envelope and the second term the interference fringes. A double slit arrangement with each of the widths of the slits being very, very small produces this interference pattern. So the very first diagram is an interference pattern with two slits which are very narrow and hence produce a very broad diffraction pattern. The slit separation controls the separation of the interference fringes.Īs the slit separation has not been changes the separation of the interference fringes stay the same. So you will note that the slit widths control the modulation of the intensity of the double slit interference pattern. Two narrow slits are placed a distance d,d from each other and light from a coherent source is shone through them onto a distant screen, forming a specific. Using two slits of this width whilst keeping the slit separation (centre to centre) the same as before results in this interference pattern. The diffraction pattern is wider than the single slit diffraction pattern shown before. Now if the slit width is halved then the diffraction pattern due to a single slit of that width looks like this. Here is the sort of pattern that you might observe on a screen: You will note that the single slit diffraction pattern controlled by the width of the slits modulates the intensity of the double slit interference pattern. If the thickness of the slit is a a, the spacing between the slits is b b, and the diffracted angle, the. Light passes through each slit and then creates a light or dark pattern depending on interference. Now if you have a double slit arrangement with slits of the width that produced the diffraction pattern above you get the following interference pattern. The double-slit experiment is the observation of the pattern that a single wavelength of light creates after passing through two slits. It is a graph of relative intensity (y-axis) against position (x-axis).Ī single slit of finite width produces a diffraction pattern. A double slit arrangement with each of the widths of the slits being very, very small produces this interference pattern.
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