All secondary waves emitted by secondary sources located on the surface of the AB wave front are damped as a result of interference, except for waves from sources located in a small section of the segment ab, perpendicular to SM. 3) emitted by a source S in a homogeneous medium is explained by the Huygens-Fresnel principle. The rectilinear propagation of a beam SM (Fig. ![]() The amplitude and phase of the wave at any point M in space is the result of the interference of waves emitted by secondary sources (Fig. have the same wavelength and constant phase difference. ![]() Huygens-Fresnel principle: all secondary sources S 1, S 2 ,…,S n located on the wave surface are coherent with each other, i.e. Represents the envelope surface of the secondary waves. New position of the wave front A 1 B 1 in time Huygens principle: each point S 1, S 2 ,…,S n of the wave front AB (Fig. To solve diffraction problems - to find the distribution on the screen of the intensities of a light wave propagating in a medium with obstacles - approximate methods based on the principles of Huygens and Huygens-Fresnel are used. 1 shows photographs of diffraction patterns from various obstacles: a) a thin wire, b) a round hole, c) a round screen. So, to observe the phenomenon of diffraction, it is necessary to fulfill certain requirements for the size of obstacles, the distances from the obstacle to the light source, and also for the power of the light source. The phenomenon of diffraction is observed at distances l from the obstacle, where D is the linear size of the obstacle, λ is the wavelength. For red light, the wavelength is λcr≈8∙10 -7 m, and for violet - λ f ≈4∙10 -7 m. ![]() light waves go around obstacles, but on condition that the dimensions of the latter are comparable to the wavelength of light. Light diffraction is the phenomenon of light deflection from rectilinear propagation in a medium with sharp inhomogeneities, i.e.
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