How to move from the aperture to the pattern (from identity to Fourier transform in a smooth way)?

In diffraction experiments, the pattern on a screen is the fourier transform of the aperture when it is a Fraunhofer diffraction (when the screen is far from the aperture). When the distance is null (screen just behind the aperture) the shape of the pattern is the shape of the aperture. so we have two operators (Id and FT) transforming aperture into...

4h

Understanding details of the chromatic aberration depicted in this simulated image from NASA

Phys.org's The detection of phosphine in Venus' clouds is a big deal, and here's how we can find out if it really is life contains part of a NASA/JPL-Caltech image which is on the cover of Aerial Platforms for the Scientific Exploration of Venus, JPL D-102569 What caught my eye is the inclusion of what I assume is chromatic aberration in the rendering...

16h

Laser spot size with pinhole

I am currently trying to find the focus of an IR laser beam by using a 300 $\mu$m pinhole. Now, when I am scanning the pinhole across the beam and plotting the pinhole position vs the laser spectrum amplitude at a given wavelength, on both $x$ and $y$ axes I obtain a profile which is well fit by a Gaussian whose width, depending on the $z$ position,...

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Is there an easy argument that magnetic permeability is almost 1 for most materials in the optical domain?

Why can we ignore the magnetization but not the electric polarization in first order? Why is the magnetic contribution so much smaller.

1d

Optics and Velocity Question from grandparent

My Grandparent asked me this question a few years ago, and I am getting around to giving him an answer, but I don't know the answer. Can anyone help? "A pickup truck is speeding along a highway at 60 mph. One man (c) is standing on the side of the highway at point A. Two men (a and b) are standing in the bed of the pickup truck. As the truck goes...

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Collimation issue with an DIY spectrograph

I am trying to make an educational echelle spectrograph using easily available materials, basically in a cardboard box. An echelle grating (36 lines/mm) needs another prism to do a cross dispersion and generate a two dimensional spectrum like the following (taken from a astro website). One can readily generate this type of spectrum using any white...

2d

Why is the colour of the black texts appearing Yellowish and Purplish?

I was revising some of the concepts from my old copies and I noticed something really weird (might not be weird for others). The texts with black pen when seen from behind the page had some yellowish and somewhat purplish appearance (as shown in figure) 1 : 2 : 3 : (the texts might not be clearly visible in the last one) . Also the third...

2d

Diffraction due to a long narrow slit

I wanted to derive an expression for intensity due to a single slit whose dimensions are 1m and a ( where a is of the order of wavelength (diffraction. For that firstly I divided the slit into infinite number of linear sources and than consider an arbitrary linear source. Now I can find the electric field contribution due to this source easily if I...

3d

Why do distant object look larger when viewed from an elevated position?

Can anyone explain the principle that results in a distant object being perceived as larger when viewed from an elevated position? eg: I notice when viewing a Shipping Vessel from the shoreline it appears significantly smaller than when viewed from an elevated position of approx 30 meters & 1/2 mile inland from the shoreline; I have also noted the...

3d

Do gravitational lenses act as prisms?

Light creates gravity, and the greater the light's frequency, the greater this gravitational effect is. It stands to reason then that light of different colors would react slightly differently to gravitational fields. Namely, bluer light would bend more than red light, causing gravitational lenses to act like prisms.

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