Diffraction optics - Diffraction gratings - Fresnel zone plates - Gabor Hologram - Order - Contact us
Interference and diffraction are the main phenomena which demonstrate the wave nature of the light. There are many optical devices, where these phenomena can be observed. Diffraction grating is one of them, which allows a beam of light to be resolved into different colors. Diffraction grating consists usually of thousands of narrow, closely spaced parallel slits (or grooves). The use of diffraction gratings DG10 and laser pointer allows these effects to be easily demonstrated and investigated at home, school, university, etc. At this website we consider the basic theory of Fraunhofer diffraction at one, double and multiple slit as well as the real experiments with diffraction gratings DG10, Fresnel zone plates FZP-01 and Gabor hologram HH-4000.
If we illuminate diffraction grating with monochromatic light of laser source, then the beam is splited into several divergent beams in accordance with parameters of grating. Particularly the angles between the beams will be inversely proportional to the period of grating. Investigating the interference pattern on the remote screen we can make a conclusion about parameters of grating. And, on the contrary, knowing the parameters of grating we can easily calculate the wavelength of light. The set DG10 contains also single slits and double slits of different width. In the figure below you can see the result of the diffraction of light at a single slit. Such an interferometric method allows the size of the minute objects (sand, dust, powder,..) to be precisely measured.
If the light is not monohromatic, then the angle of diffraction depends upon the wavelength. In this case the spectrums of radiation in different orders will appear instead of the beams. Let us place the diffraction grating DG-2/1-4000 in front of objective glass of photo-camera and will take a photo of the candle flame. We see that the picture is multiplexing. If the central image coincide with the one without the grating, then the images in higher orders are dissolved in spectrum similar to rainbow. This property of diffraction is used for investigation of the spectrums of the optical radiation.
If the light waves from different slits are interfere in phase, then we observe an interferometric maximum. The same effect can be observed if we substitute the slits by transparent and opaque rings. The light waves from these rings must reach some point in phase. In this point we shall observe maximum of intensity. Such system of the rings ( shown in the left side of the image below) is called Fresnel zone plate and the point of maximum is called focus point of such a plate. The amplitude of light in focus of zone plate is proportional to amount of the open (transparent) rings. Unlike a standard lens, a zone plate produces subsidiary intensity maxima along the axis of the plate at odd fractions (f/3, f/5, f/7, etc.), though these are less intense than the principal focus. If the zone plate can be constructed such that the opacity varies in a gradual, sinusoidal manner, the resulting diffraction causes only a single focal point to be formed. This type of zone plate pattern is the equivalent of a transmission Gabor hologram shown in the right side of the image below.
You can order diffraction gratings DG10, Fresnel zone plates FZP-01 and Gabor hologram HH-4000 with KAGI online payment processing system and use them for educational and scientific purposes. We shall send the ordered items to you by mail after the payment confirmation.
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