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Step 4Diffraction grating
Overview:
Diffraction gratings are a wonderful pieces of optical technology. They allow us to manipulate light based on its wave properties (rather than the particle or ray properties). The classical physics demonstration of diffraction goes something like this: send a beam of light at a dual-slit structure (two small holes) so that as the light passes through it diffracts and creates an interference pattern characterized by bright and dark regions, akin to the peaks and valleys of a wave. Diffraction is most pronounced when the object the light is striking has similar dimensions to the wavelength of the light, if we consider the wavelength of red light is around 650nm then the microscopic diffraction structure is tiny, we're talking sub-millimeter (micron) to get dramatic effects
What's a diffraction grating?:
So if you want to diffract light, you need a diffraction grating. Perhaps the easiest way to visualize a diffraction grating is to think of a picket fence, except many orders of magnitude smaller. It's a periodic structure (which just means its repeating along its length) and so if we shine light through the slits in this picket fence, the passing waves will interfere and add and subtract to create a unique projection pattern. By changing the period (frequency) of the posts in the fence then we can also change the intereference pattern as well. This is metric is often mentioned as the number of "line pairs/inch"
Where do you see diffraction?:
Diffraction is all around us, the most common place you've probably noticed it is on the surface of a CD or a hologram. The rainbow of colors is created by the diffracting surface composed of tiny ridges and troughs. Recently there's been an emergence of rainbow glasses that create a sort of "color explosion" when you look at light sources. Those are simply thin pieces of diffraction grating with small ridges that have been most likely embossed onto the plastic surface. You also might have seen "star" caps for laser pointers. These are also small pieces of diffraction grating that have been glued into a laser pointer cap.
Why is it in the Laser Ball?
Why have just one beam per laser when you can have many? It's a laser party so bring your friends! The diffraction grating will distribute the optical energy from the laser into different spatial frequencies so rather than just creating a beam directly on-axis, multiple beams are created at specific frequencies (i.e. angles) matched to the periodic structure of the grating.
Check out these links for more information on diffraction gratings
Diffraction gratings are a wonderful pieces of optical technology. They allow us to manipulate light based on its wave properties (rather than the particle or ray properties). The classical physics demonstration of diffraction goes something like this: send a beam of light at a dual-slit structure (two small holes) so that as the light passes through it diffracts and creates an interference pattern characterized by bright and dark regions, akin to the peaks and valleys of a wave. Diffraction is most pronounced when the object the light is striking has similar dimensions to the wavelength of the light, if we consider the wavelength of red light is around 650nm then the microscopic diffraction structure is tiny, we're talking sub-millimeter (micron) to get dramatic effects
What's a diffraction grating?:
So if you want to diffract light, you need a diffraction grating. Perhaps the easiest way to visualize a diffraction grating is to think of a picket fence, except many orders of magnitude smaller. It's a periodic structure (which just means its repeating along its length) and so if we shine light through the slits in this picket fence, the passing waves will interfere and add and subtract to create a unique projection pattern. By changing the period (frequency) of the posts in the fence then we can also change the intereference pattern as well. This is metric is often mentioned as the number of "line pairs/inch"
Where do you see diffraction?:
Diffraction is all around us, the most common place you've probably noticed it is on the surface of a CD or a hologram. The rainbow of colors is created by the diffracting surface composed of tiny ridges and troughs. Recently there's been an emergence of rainbow glasses that create a sort of "color explosion" when you look at light sources. Those are simply thin pieces of diffraction grating with small ridges that have been most likely embossed onto the plastic surface. You also might have seen "star" caps for laser pointers. These are also small pieces of diffraction grating that have been glued into a laser pointer cap.
Why is it in the Laser Ball?
Why have just one beam per laser when you can have many? It's a laser party so bring your friends! The diffraction grating will distribute the optical energy from the laser into different spatial frequencies so rather than just creating a beam directly on-axis, multiple beams are created at specific frequencies (i.e. angles) matched to the periodic structure of the grating.
Check out these links for more information on diffraction gratings
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By the way if you buy the same gratings the grating itself is much larger between the layers of paper you have to dissolve it in water and clean the foil afterwards with some alcohol then you get a foil approximately around 4,5 x 5 cm.