Using the Fourier Transform (similar to our study of sound and harmonics) we can come up with “optical frequencies.” So the diffraction “pattern” produced by a grating is actually the Fourier Transform of the geometry of that physical grating. The mathematics describing the pattern observed does depend on the geometry of the grating. The light which will be reflected due to constructive interference depends on the wavelength and the thickness of the film (the the index of refraction in the film).Ī diffraction grating is a series of slits which we can use to create a series of spaced out fringes. You can produce the nice colored fringes that you often see on gasoline slicks or soap bubbles. Perhaps the key thing to take away from this equation is that for larger wavelengths the degree of spreading is greater.Īn interesting phenomena called thin film interference happens when light interference with itself by reflecting between surfaces of a film. So for small angles we can get away with using one equation for both of these phenomena. We can see for the double slit interference, things are similar but not exactly the same The equation for single slit diffraction can be found at hyperphysics with a nice explanation of the concepts. Learn the detailed behavior of light as it encounters objects. Where λ is wavelength, d is the slit separation, x is the fringe spacing, and L is the distance to the screen. Refraction (bending), dispersion (splitting into colors) and diffraction (spreading out) are ways light reacts when interrupted. When light is irradiated onto a diffraction grating, the effect of the grooves causes a diffraction of light, which allows the incident light to be divided according to its wavelength. Assignment-II MA - Assignment topic-Differential & Integral Calculus of single variable. A diffraction grating is an optical element fabricated on a glass substrate with finely spaced grooves at equal intervals. Assignment-I MA - Assignment topic-Infinite series. Your workbook will lead you to believe you can swap the equation between these two related, but different phenomena. Recommended for you Document continues below. However, the equations which describe the location of fringes, or anti-nodes are different, and the physical underpinnings of these equations are different. Interference and diffraction are different phenomena, although there are significant connection. This is known as Young’s Principle, who first did several experiments with slits, and is well known for observing the interference of slight using a 2 slit experiment. The amount of bending depends on the relative size of the wavelength of light to the size of the opening. It appears as if the slit itself is the source of circular waves as opposed to the original source. The definition of diffraction is the spreading of waves as they pass through or around an obstacle. Diffraction is the slight bending of light as it passes around the edge of an object.
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