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I am not totally sure of this answer, which is why I asked the question. However, I think the answer is that only relatively short wavelengths can pass through an annular aperture. Specifically, I think that if the outer radius of the annulus is R and the width is W, where W << R, the maximum wavelength that passes through is approximately 2R ...


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You can attract metal with static electricity. Consider the text-book example of a conducting sphere vs. a dielectric sphere in an electric field. Let's assume the field is homogeneous. This field polarizes both spheres, but in different ways: Conducting sphere: The free electrons rearrange themselves on the surface until the total electric field is ...


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The fact is that metals do get polarized but in a different way. Since electrons are rather free, they distribute themselves along the frontier of the system, being attracted by the field. But they do so in such a way that the field becomes zero inside the metal, because the contribution from the external field and these electrons cancel each other. You ...


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You can make beams of light that have orbital as well spin angular momentum and they can go through an annular aperture. So circular versus linear isn't enough. Linear has the phase advance orthogonal to the advancement with the polarization at a fixed angle. Circular has the polarization rotate but with an annular filter you can give the wavefront a twist ...


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This is a typical matrix for an optically active element that rotates the light polarisation. A cuvette of water with sugar will do the job. Proportional to the sugar concentration, you can obtain arbitrary wave rotation. Note that the U matrix has imaginary eigenvectors (1+i)/sqrt(2) and (1-i)/sqrt(2). Accordingly, unlike λ/4 plates, the eigenwaves of such ...


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The light that we receive directly from the Sun is emitted in the photosphere, travels in a straight line through the atmosphere to us, and is unpolarised. The photosphere is a region covering the whole surface of the Sun and is also of order hundreds of km thick. Thus the light received at a point on Earth is a pseudo-random mixture from many points on the ...



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