Diffraction definition5/17/2023 ![]() When the sources are incoherent or multi-chromatic - or worse, both (which is the case with white light) - the bands produced are indistinguishably muddled and not as uniform and distinct. While light does experience interference, it is only conspicuous when the two sources of light are both monochromatic - emitting light of a single wavelength - and coherent - emitting identical waves of a constant phase difference. However, before we can understand how the slit diffracts the light, let’s make one thing clear. The pattern produced by a diffracted laser. ![]() The pattern is called a diffraction pattern, because the light with which it is painted is diffracted. What’s wonderful is that the pattern can be generated with a single slit as well. However, in a pattern generated by a single slit, unlike the pattern generated by two slits, the intensity of light is not evenly distributed. The addition causes the luminosity of the region to double, whereas the negation renders the region utterly dark. Young immediately realized that when the two waves are squeezed between the slits, a bright band is produced when the peak of one ripple interferes constructively with or is added to the peak of another ripple, while a dark band is produced when the peak of a ripple interferes destructively with or negates another ripple. Only waves interfering with each other can form such a pattern. The discovery vindicated Huygens, as light cannot bend or flow around an obstacle unless it obeys his principle. What the squeezed lights illuminated on a screen ahead of them is now called an interference pattern – a uniform, alternating pattern of bright and dark bands. Reflection according to Huygens’ principle.Ī century later, it was the British polymath Thomas Young who successfully demonstrated how light behaves like ripples in a pond by forcing light to squeeze through two adjacent slits. He failed to prove his claims experimentally. However, Huygens could never demonstrate the wave nature of light. He also elegantly explained the occurrence of optical phenomena, such as reflection and refraction, with his wave theory of light. He postulated what is now called Huygens’ principle: every point on a wave of light is a source of secondary waves that travel at the same speed as light. ![]() A detailed understanding of the phenomenon of diffraction will reveal why this is the case.Ĭontrary to Newton’s belief, Christiaan Huygens, in the 17 th century, suggested that light doesn’t behave like a particle, but rather like a wave. However, does the stream of light always flow around the obstacle? No, particularly when the obstacle is too large. Diffraction is why we can detect a source that is situated beyond the curve or why the edges of a cloud obscuring the Sun still gleam, accentuating what we call its silver lining. The light, like water, flows around the obstacle to reach our eyes. It is diffraction that makes the light radiated by a source detectable, even when its path is obstructed by an obstacle. A diffraction grating is an obstacle with many slits that diffracts waves in a particular pattern.ĭiffraction, along with interference and polarization, is an indisputable proof of the wave nature of light. Diffraction is the bending of waves around an obstacle.
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