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Interference and Diffraction 14.1 Superposition of Waves Consider a region in space where two or more waves pass through at the same time. According to the superposition principle, the net displacement is simply given by the vector or the algebraic sum of the individual displacements. Interference is the
1 Huygens’ principle. Diffraction refers to what happens to a wave when it hits an obstacle. The key to understanding diffraction is a very simple observation first due to Huygens in 1678. Say a wave arrives at an opaque screen with a little hole in it.
Diffraction is the concept that is explained using Huygens’s Principle, and is defined as the bending of a wave around the edges of an opening or an obstacle. This principle can be used to define reflection, as shown in the figure.
Hyugens-Fresnel principle. If one perturbs a plane wavefront, the Huygens wavelets will no longer constructively interfere at all points in space. Adding the wavelets by physical optics explains why light can turn corners and create fringes around images of objects.
Huygens Principle and Diffraction. Every point on a propagating wavefront becomes a secondary source of spherical wavelets. All these wavelets form the envelope of the next wavefront. Diffraction – Bending of light into the shadow regions (wavelength, λ, of the order of obstacles)
The study of the interference and diffraction of light is referred to as wave optics or physical optics, to distinguish it from geometrical optics, which deals with the straight-line motion of light and its reflection and refraction. In this chapter, we will study the wave nature of light.
But the principle is all the same: we are only adding waves at different phases. As another important application of diffraction, we may mention the following. We used a grating and we saw the diffracted image on the screen.
