![]() ![]() ![]() The most colorful examples of diffraction are those involving light for example, the closely spaced tracks on a CD or DVD act as a diffraction grating to form the familiar rainbow pattern we see when looking at a disk. Now try some multiple choice questions on diffraction. The effects of diffraction can be regularly seen in everyday life. Now look at the page on Diffraction Gratings Questions It can be shown theoretically that using light of wavelength, the width W c of the central fringe observed on a screen at distance D from the slit is given by: Using an adjustable slit, the observations show that making the slit narrower makes the fringes wider. Using different sources of monochromatic light in turn, the observations show that the greater the wavelength, the wider the fringes, The outer fringes are much less intense than the central fringe. The peak intensity of each fringe decreases with distance from the centre,Įach of the outer fringes is the same width, The amount of diffraction that occurs depends on the wavelength of the light, and shorter wavelengths are diffracted at a greater angle than longer ones. The central fringe is twice as wide as each of the outer fringes (measured from minimum to minimum intensity), The central fringe is twice as wide as the others. The intensity of the fringes is greatest at the centre of the central fringe. The pattern shows a central bright fringe with further dark and bright fringes either side. When the incident light is polarised in any arbitrary azimuth, the diffracted light is found to exhibit elliptic polarisation. You see 'fringes' - bands of light (which from a laser are red) and no light (which on the diagram are shown in black. The diffracted light forms a pattern that can be observed on a white screen. These breaks are due to waves diffracted by adjacent sections on the gap being out of phase and cancelling each other out in certain directions.ĭiffraction of light by a single slit can be demonstrated by directing a parallel beam of light at the slit (a laser is good to use). This arrangement shows that the diffracted waves become more circular if:Ĭlose examination of the diffracted waves reveals that the each diffracted wavefront has breaks either side of the centre. Therefore, because a telescope is much wider than the eye pupil, much less diffraction occurs when using a telescope than when observing with the unaided eye.ĭiffraction of water waves through a gap can be observed using a ripple tank. This is partly because less diffraction occurs when waves pass through a wide gap than through a narrow gap. This general property of all waves is very important in the design of optical instruments, such as cameras, microscopes and telescopes.įor example, when a telescope is used to observe planets, we can often see features that are not evident when observed directly. What does diffraction look like When light diffracts off of the edge of an object, it creates a pattern of light referred to as a diffraction pattern. Particles would not do that so diffraction is evidence of the wave nature of light. A Level and AS level - UK KS 5 (Age 16 - 18)ĭiffraction is the spreading of waves when they pass through a gap or by an edge.GCSE and 'O' Level - UK KS4 (Age 14 - 16). ![]()
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