![]() ![]() Each point on the wall has a different distance to each slit a different number of wavelengths fit in those two paths.Destructive interference occurs when waves interfere with each other crest-to-trough (peak-to-valley) and are exactly out of phase with each other. Constructive interference occurs when waves interfere with each other crest-to-crest and the waves are exactly in phase with each other. ![]() The light that appears on the wall behind the slits is partially absorbed by the wall, a characteristic of a particle. The wave characteristics of light cause the light to pass through the slits and interfere with each other, producing the light and dark areas on the wall behind the slits.We will examine in later atoms single slit diffraction and double slit diffraction, but for now it is just important that we understand the basic concept of diffraction.Īs we explained in the previous paragraph, diffraction is defined as the bending of a wave around the edges of an opening or an obstacle. When light passes through much smaller openings, called slits, Huygens's principle shows that light bends similar to the way sound does, just on a much smaller scale. However, if that person where to open their door while playing music, you could hear it not only when directly in front of the door opening, but also on a considerable distance down the hall to either side. If someone is playing music in their room, with the door closed, you might not be able to hear it while walking past the room. Although this principle applies to all types of waves, it is easier to explain using sound waves, since sound waves have longer wavelengths. This principle is actually something you have seen or experienced often, but just don't realize. These effects were explained in 1816 by French physicist Augustin-Jean Fresnel. Diffraction effects are the deviations from rectilinear propagation that occurs when light encounters edges, screens and apertures. He could not, however, explain what is commonly known as diffraction effects. He was able to come up with an explanation of the linear and spherical wave propagation, and derive the laws of reflection and refraction (covered in previous atoms ) using this principle. ![]() shows secondary waves traveling forward from their point of origin. The sum of the secondary waves (waves that are a result of the disturbance) determines the form of the new wave. In 1678, he proposed that every point that a luminous disturbance touches becomes itself a source of a spherical wave. The new wavefront is a line tangent to all of the wavelets.Ĭhristiaan Huygens was a Dutch scientist who developed a useful technique for determining how and where waves propagate. These wavelets spread out in the forward direction, at the same speed as the source wave. The Huygens-Fresnel principle states that every point on a wavefront is a source of wavelets.
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