If the first dark fringe appears at an angle 30 °, find the slit width. Fraunhofer diffraction at a single slit is performed using a 700 nm light.
The incident waves are not parallel.įraunhofer Diffraction: The light source and the screen both are infinitely away from the slit such that the incident light rays are parallel.ġ. The slit width should be comparable to the wavelength of incident light.įresnel Diffraction: The light source and the screen both are at finite distances from the slit. The incident light should be monochromatic. It can be inferred from this behaviour that light bends more as the dimension of the aperture becomes smaller. If the slit width decreases, the central maximum widens, and if the slit width increases, it narrows down. The width of the central maximum in the diffraction formula is inversely proportional to the slit width. Here, θ is the angle made with the original direction of light.
If a monochromatic light of wavelength λ falls on a slit of width a, the intensity on a screen at a distance L from the slit can be expressed as a function of θ. Due to the path difference, they arrive with different phases and interfere constructively or destructively. Each wavelet travels a different distance to reach any point on the screen. These wavelets start out in phase and propagate in all directions. Unlike the double-slit diffraction pattern, the width and intensity in the single-slit diffraction pattern reduce as we move away from the central maximum.Įxplanation of The Phenomenon and Diffraction FormulaĪccording to Huygens’ principle, when light is incident on the slit, secondary wavelets generate from each point. In a single slit experiment, monochromatic light is passed through one slit of finite width and a similar pattern is observed on the screen. All the bright fringes have the same intensity and width. The waves, after passing through each slit, superimpose to give an alternate bright and dark distribution on a distant screen. In this experiment, monochromatic light is shone on two narrow slits. Thomas Young’s double-slit experiment, performed in 1801, demonstrates the wave nature of light. This phenomenon is known as single slit diffraction. If light is incident on a slit having a width comparable to the wavelength of light, an alternating dark and bright pattern can be seen if a screen is placed in front of the slit. The effect becomes significant when light passes through an aperture having a dimension comparable to the wavelength of light. This suggests that light bends around a sharp corner. When light is incident on the sharp edge of an obstacle, a faint illumination can be found within the geometrical shadow of the obstacle.
According to Huygens’ principle, when light is incident on the slit, secondary wavelets generate from each point. This phenomenon is called the single slit diffraction. When light is incident on a slit, with a size comparable to the wavelength of light, an alternating dark and bright pattern can be observed. Fraunhofer was the son of a maker of decorative glasses and mirrors in Bavaria, while Fresnel was the son of an architect in Normandy.ĭiffraction is the bending of light around the sharp corner of an obstacle. These two weak youngsters were still struggling to get educated.
This was possible in the early nineteenth century when two great scientists were struggling in their lives separately in Italy and Germany. Diffraction is the line of study that helped in the development of precise spectrometers, hence helping Astronomy take great leaps.
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