Due to this reason, the same sound wave can bend around obstacles and also tend to disperse in different directions after passing through a hole or crevice. Diffraction can also be said to have a dual nature. In fact, one can hear sounds around barriers and corners through a process that involves both reflection and diffraction. Thus, diffraction is the cause of violation of law of linear propagation of light or sound.ĭo you think it would be impossible to hear a sound if sound waves could not be diffracted? In some instances, the answer would be yes and in others the answer may be no. Same thing happens in case of light also but the level of diffraction in light is very small. After diffraction through a small hole, the sound is reaching the receiver. Sound from a source which is placed behind the screen / wall is creating sound waves. In the figure above, we see a receiver standing on the other side of a wall/ screen. Hearing voice while beings far apart from source is an example of diffraction of sound waves. It is due to process of diffraction that we are able to see/hear certain things which would not have been possible otherwise. Diffraction describes the movement in wave’s direction as it bends around an obstacle. Bending from one medium to the other medium, reflection off surfaces, and travelling through objects are some of the properties that waves possess. We can see this process in both light and sound waves. We, therefore, have constructive interference, which produces a maximum (the brighter parts in the image) at those points that are multiples of half the wavelength.Diffraction is a phenomenon that we experience in our day to day life. We can read it as n times the wavelength, and this quantity is equal to the length of the aperture multiplied by the sine of the angle of incidence θ, in this case, π/2. Here, n = 0, 1, 2 is used to indicate the integer multiples of the wavelength. We use the following formula to determine where the destructive interference occurs: What happens is that the waves interfere with each other destructively according to the width d of the slit and the wavelength λ. If we increase the wavelength of the wave, the difference between maximums and minimums is no longer evident. A wave passing through an aperture whose aperture length d is greater than the wavelength λ. In the centre of the aperture, when its length d is greater than the wavelength λ, part of the wave passes through unaltered, creating a maximum beyond it.įigure 2. The dimension of the aperture affects its interaction with the wave. Notice how the wave front briefly becomes circular but returns to its original linear shape as it leaves the obstacles behind. The arrows indicate the direction of the propagation, while the dotted lines are the wave fronts before and after the obstacle. A wave is propagating towards an aperture. The irregularities are caused by the gate’s edges.įigure 1. The wave forms parallel lines before the obstacle but irregular ones while passing through and beyond the gate’s opening. Keeping the same example but exchanging the rock for an open gate, we experience the same behaviour. The bigger the rock, the bigger the irregularity. In these conditions, parallel waves are formed where there is nothing to block them, while right behind the rock, the shape of the waves becomes irregular. An example is a calm breeze moving the water around a rock that cuts through the surface of a lake. When a wave propagates across an object, there is an interaction between the two. The way their propagation is affected by the object or the opening depends on the dimensions of the obstacle. Total Internal Reflection in Optical Fibreĭiffraction is a phenomenon that affects waves when they encounter an object or an opening along their path of propagation.Newton’s and Huygens’ Theories of Light.Einstein's Theory of Special Relativity.Electromagnetic Radiation and Quantum Phenomena.Galileo's Leaning Tower of Pisa Experiment.Magnetic Flux and Magnetic Flux Linkage.
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