![]() Overall, the results indicate that the recognition of interference and diffraction patterns is quite demanding for students, suggesting that more attention should be paid to observing and understanding basic wave optics phenomena. Additionally, eye tracking revealed that students who identified patterns correctly attended more the correct pattern than other options, thus corroborating previous findings. Eye-tracking data suggested that even students who incorrectly answered this question were aware that the diffraction grating separates white light into colors. The easiest task for students was recognizing the diffraction pattern of white light on an optical grating. Identification of the single-slit diffraction pattern was easier probably due to its distinguishable central maximum. Most students had difficulties with recognizing double-slit interference pattern and diffraction grating pattern of monochromatic light. ![]() ![]() Eye movements of high-school students were measured while they were identifying patterns produced by monochromatic light on a double slit, single slit, and diffraction grating, and by white light on a diffraction grating. In this study, we investigated if students could recognize typical interference and diffraction patterns at all. The width of diffraction fringes is always unequal.Previous studies have demonstrated that students have difficulties in applying the wave model of light to explain single-slit diffraction and double-slit interference patterns. ![]() The width of interference fringes may or may not be equal. The intensity of minima is never zero and hence there is poor contrast between bright and dark bands. The intensity of minima is generally zero, and there is a good contrast between bright and dark fringes. In the case of diffraction, the bright bands are not of the same intensity. In the case of interference, all bright bands are of the same intensity. Interference is due to the superposition of two different wavetrains coming from two coherent sources.ĭiffraction is due to the superposition of secondary wavelets from different parts of the same wavefront. Interference and Diffraction Superposition of wave: When two or more wave travelling through the particles of medium arrive at a point of medium simultaneously each wave produces its own displacement independent to each other then, the resultant displacement at that point is equal to the vector sum of displacement due to all wave. According to Fresnel, diffraction occurs due to mutual interference of secondary wavelets which are not blocked by obstacle.įollowing are the points of difference between Interference and Diffraction of Light- Interference For visible light, the diffraction phenomenon is not so common, because the wavelength of visible light is very small ( ≅10 -6m) and obstacles of this size are hardly available. In the case of sound waves and radio waves, diffraction is observed readily because the wavelength of these waves is large and obstacles of this size are readily available. Also, the diffraction becomes much more pronounced, when the size of the obstacle is comparable to the wavelength of light. ![]() Due to this, the light spreads into the regions of the geometrical shadow of the obstacle. A diffraction grating can be manufactured by scratching glass with a sharp tool to form a number of precisely positioned parallel lines, which act like slits. At the points, where the resultant intensity of light is maximum, Interference is said to be constructive and at points, where the resultant intensity of light is minimum, the interference is said to be destructive.ĭiffraction- It is the phenomenon of bending of light around the corners of an obstacle in the path of light. An interference pattern is created that is very similar to the one formed by double-slit diffraction (see Figure 17.8 and Figure 17.9 ). Interference- Interference of light is the phenomenon of redistribution of light energy due to the superposition of light waves from two coherent sources. ![]()
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