# Tagged Questions

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### Where do rays that are not marginal or principal get stopped?

The picture is from an MIT lecture but the concepts are explained in many optical texts. The chief/principal rays go through the center of the aperture stop, hit the edge of the field stop, and the ...
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### What does it mean for a Fresnel lens to have two finite conjugates?

I'm in a situation where I need to reverse engineer a product that my company already manufactures and sells, but it wasdesigned too long ago for anyone to remember. It uses a Fresnel lens with the ...
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### Colour of artifacts in a lens flare

I'm adding a lens flare to an illustration; which got me thinking: Are the colours of the artifacts (hexagonal/circular) which appear in a lens flares purely random, or much like a rainbow (...
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### Optical bandpass filter at focal point of lens

Optical bandpass filters are designed for a particular angle of incidence (AOI), e.g. see Fig 4 here. However that is for the ray picture of light. Imagine I have a thin bandpass filter positioned ...
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### General proof of formulas of geometric optics?

In most lf textbooks formulas of geometric optics like lens maker formula and base formula for that are proven (or rather verified from my point of view) by taking specific case (ray diagram) and ...
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### How to calculate the focal length of spherical shell (zero meniscus lens)

I can get my head around the optics of a spherical shell (a meniscus lens that neither diverge nor converge, being neither positive nor negative etc). I don’t see how I can describe in a formula how ...
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### Minimal size of an optical lens

Is the minimal size of an optical lens (diameter, width and curvature) limited by the wavelength of the incident light?
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### opaque to transparent based on distance of object?

If we look through a transparent glass window of an apartment, from a distance in day light, we can’t see what or who is inside. All the light is reflected off the surface of the transparent glass ...
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### Double Fraunhofer , Fourier transform to the image plane?

Consider the diagram below: I know that from Franhofer diffraction we have: $$u_f(x_f)\propto \int u_o(x_o) e^{-k\frac{x_f}{f}x_o} dx_o$$ Assuming small angles. I also know that $u_i(x_i)$ is ...
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### Broad Spectrum Contact Lenses - How Soon?

Given the amazing advances in metamaterials, how soon will we have the means to view a broad spectrum of electromagnetic radiation (IR through UV) by having it faithfully compressed into the range of ...
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### Coordinate Equation of a curve which bends all the parallel incoming rays from infinity towards a single point

How should i proceed on to find the coordinate equation of a curve such that it bends all the parallel rays coming from infinity towards a single point. Yes I know that it would be a 2nd degree ...
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### Sun light collimation

Is it possible to make sun light collimated in such a way, to increase energy density and keep it more less parallel? like on the Earth we have intensity of sun approximately 1300 watt/m2. If we use ...
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### addition of two lenses with a finite separation in between

Suppose there are two lenses with focal length $f_1$ and $f_2$ respectively. The effective focal length $f$ when they are combined is $1/f=1/f_1+1/f_2$, but this formula assumes the separation between ...
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### Focal length value for infrared camera

I always thought that the 5 mega pixel camera attached to my Android tablet wasn't worthy of seeing the infrared. But I was wrong! The infrared led protruding from my circuit happily shows up it's ...
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### Why do Photochromatic lenses react to temperature changes?

So, I'm aware that Photochromatic lenses are affected differently due to different ambient temperatures. From what I've read it seems that the molecules rearrange their structures slowly in cold ...
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### Splitting an image in a lens into two sources?

Is it possible to project an image of light that passes into a lens onto two surfaces without affecting the image?
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### How to determine the distance between the principal planes?

How to determine the distance between the principal planes ? If you know the lentgh of both focii, $\overline{FH}$, $\overline{F'H'}$ and additionally the distances $\overline{E1H}, \overline{H'E2}$,...
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### The image of an object through a curved surface

We have a curved surface, separating two different medium, with refractive index n1 and n2. We know the radius R of the curve,then how can we find the position v of the image? I read that the ...
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### Lens formula and Lens maker's formula

When we derive the formula for lens and lens maker's formula using the formula for refraction at spherical interface $$\mu_2/v - \mu_1/u = (\mu_2-\mu_1)/R$$ we put $u$ to be $-u$ as it is on the left ...
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### Balance lens tilt aberration

Given a doublet (singlet in reference figure), if the rays enter at an angle with respect to the origin axis, we would see a shift of focal length for blue and red. A known optical jitter How could ...
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### Difference between the increase in optical path due to refraction and that due to reflection

If we place two glass plates of refractive index n and each having thickness t,on the way of a light ray the increase in optical path becomes (S2P-S1P)=2(n-1)t due to refraction through them,and the ...
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### What is this area on a lens seen from extreme angle?

This has been a secret to me since childhood: a normal lens made of glass in front of a white LCD screen (shot with a crappy phone camera)... ...if viewed from an extreme angle shows a very ...