Questions tagged [lenses]

A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction.

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42 views

How can I find the angle after the last lens from in the last lens?

I want to find the angle after the last lens when the beam diffracts. How can I do that? Is it the field of view? But for the field of view formula it takes account the size of the sensor. I want to ...
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92 views

Image reconstruction / generation in the human eye

It is well known how an image is produced in general: You need at least two rays (in geometric optics) to form it, see the image next: But I wonder about these images: As you can see, in the upper ...
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74 views

Lens with different mediums [closed]

Assuming parallel rays are incident, I basically want to derive a general equation for lenses with different mediums. Can we use the effective focal length method? Also, while deriving the equation, ...
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30 views

Adapting a lens to a projector

I want to project an image coming from a digital micro-mirror device (dlp projector) through a camera lens system (c-mount). Due to physical constraints, my lens is mounted at least 50mm from the ...
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40 views

Effect of a cylindrical lens in front of a diffractive optical element (DOE) and 5mW red laser

I want to expand the image formed by a grid pattern diffractive optical element (DOE). I will be using a 5mW red (650nm) laser. I thought maybe putting a cylindrical lens in front might spread the ...
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23 views

Lens and plane mirror: inverted or not?

In a situation like this, I understood that the focal length is half of that of the original lens. However, I don't know whether its image is inverted or not. In this situation, will the image be ...
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30 views

Focal length of concave mirror with water

I want to find the focal length of mirror in the picture below. I know that beetween air and water the refraction happens, then light passes throuh water with thickness $d$, then it bounces on the ...
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34 views

Magnification of a system of lenses

I have a lens system consisting of 7 elements. However, I cannot take the system apart to measure the distance between them or their focal lengths. I do, however, know the effective focal length of ...
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20 views

Would being nearsighted/astigmatic lead to seeing diffraction patterns from white light?

I am nearsighted with a prescription of greater than -10 diopters and an astigmatism. When I take off my glasses or contacts and look at a source of white light such as a lamp, then I observe white ...
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81 views

Does a lens always act as a Fourier transform?

I understand that putting a lens behind an aperture at the distance 1f, it will "get" the diffraction pattern to appear in the back focal plane. In this case the FT of the aperture plane ...
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36 views

Fraunhofer diffraction and lens

[This image is collected from the Fraunhofer diffraction article of wikipedia] Fraunhofer diffraction and lenses In Fraunhofer diffraction the source is infinitely away from the lens and screen which ...
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is it possible to replace the welding machine with a light beam?

Using mirrors, lenses, and a battery of any power? Yes, it can be expensive, yes, it can be inefficient, but it is absolutely not important. Not about laser
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When determining the position of the principal points of a lens system from $f=PF$, should one always go towards the lens system?

for an optics lab, I need to determine the position of the cardinal points of a telephoto lens. I got the focal points determined experimentally, and the focal length of the system f=200mm, which was ...
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Question regarding refraction of light through a spherical lens

I know that the divergence of a light ray through a biconcave lens can be explained through successive refractions inside the lens, somewhat like what is shown in the diagram (where the pink line and ...
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Why does the sun not burn your retinas when in peripheral vision?

After going to the ophthalmologist and having bright lights shone in my eyes, I was thinking about how the brightness only hurts when I looked at the light. When it was in my peripheral vision, it ...
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131 views

Interference pattern due to a thin prism and a lens

We have a setup like this where a converging lens placed between inclined face of thin glass wedge and a screen. The screen is parallel to the inclined face of the wedge and the optical axis of the ...
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Does it makes sense to interpret the Point Spread Function as a volumetric density of energy?

The Point Spread Function (PSF) of an imaging system is its impulse response. Therefore $$ I(x,y,z) = \left[O \star PSF\right](x,y,z) $$ where $I$ is the image, $O$ is the object, and $\star$ is the ...
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Does spectacle user able to guess correct distance of object?

It is said in many numericals like a man has near point 100 cm than he need a convex lens that can project a img of obj kept at 25cm at 100cm so that he can watch it clearly! Then my question is, Does ...
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80 views

Is there a difference between a diffraction pattern and an interference pattern?

I am in high school at the moment and I am revising a section on waves. I am slightly confused by some things in our notes, which I would like to ask about. We looked at Young’s double slit experiment,...
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33 views

A problem on Equivalent focal length

This is a combination of three lenses whose equivalent focal length is to be found. Solving for the focal length of the first lens was not a problem, it was obtained by applying Lens-Maker's Formula ...
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77 views

First and second focus of a convex lens

Referring to this, I have a confusion whether the first focus is always left of a convex lens? Can it not be on the right? The definition of first focus is : “that point on the principal axis of the ...
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Newton's rings due to two equiconvex lens

An equiconvex lens is placed on another equiconvex lens. The radii of curvatures of the two surfaces of the upper lens are $R_1$ and those of the lower lens are $R_2$. The waves reflected from the ...
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54 views

What’s the difference between a plano-convex lens and a convex-plano?

I guess they’re essentially the same but one (plano-convex) has the plane surface to the incoming ray and then the convex or spherical surface while the convex-plano have the spherical surface to the ...
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What type of lens is this?

My teacher taught me that there are two families of lenses - convex family (the lenses which are thicker at the centre and thinner at the apices) and concave family (the lenses which are thinner at ...
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118 views

Why I see everything which is red in 3D with my prescription eyeglasses?

I have prescription eyeglasses with -1.5D power (Myopia). I have been wearing eyeglasses for past 5 years and recently changed to blue light filter ones. Now I recognise everything red in colour as a ...
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Why are the lenses of a Keplerian Telescope positioned the sum of their focal points apart?

I am currently designing an extremely simple Keplerian telescope and am confused as to why many explanations say that the objective lens and eyepiece lens are positioned a distance of the sum of their ...
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35 views

How should the 4 lenses in this binocular eyepiece be mounted?

I have an old 8x25 compact binocular of the make StarLux. I disassembled it for cleaning, but unfortunately the lenses in the ocular (eyepiece) sort of dropped out of the tube before I had a chance to ...
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40 views

Can diopters be added for glasses? or is it more complicated?

I am using glasses for myopia and in the past couple years I've been adding reading glasses for when I'm on the computer. The reading glasses add +0.75. I wear one pair on top of each other! it's not ...
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83 views

What's limiting the field of view of a lens

An ideal lens with finite aperture leads to the formation of an image in the image plane as \begin{equation}g(x, y) = \int \text{psf}(x/\lambda d - x', y/\lambda d -y') f(x', y') dx'dy',\end{equation} ...
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Double slit followed by lens

If the focal length of the second lens is $f$, prove that maxima are located at $y_m$, where $y_m = mf{\lambda}/a$. I have tried to use the equation of lens but I am not sure what should I put as the ...
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137 views

How would the focal length of a convex lens change if it is submerged in a liquid of higher optical density? [closed]

We know that when a convex glass lens is submerged under water, it's focal length increases- As refractive index of the pair of media reduces and the light rays deviate less to meet the principal axis ...
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Lens Design 60GHz Radar

I'm trying to design a lens for a 60GHz radar chip however rather than focusing the radar beam I'd like to widen it to a specific width. Also, the radar antenna has a main beam width that is larger ...
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45 views

Magnification of a compound microscope

Whilst finding the magnification of a compound microscope, we multiply the linear magnification of the objective with the angular magnification of the eyepiece. This gives us the angular magnification ...
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In Fourier Optics, does the distance between a lens and a diffraction apparatus have an impact on the shape of fringes?

In our optics lectures we were given the following explanation as to how to deal with a lens as a fourier element: We are told that to find the intensity function of the diffracted light, we first ...
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Estimate off axis source light loss with lens?

Issue: I'm trying to measure some light sources very accurately. I'm finding an issue with light detected by the camera falls off as you move off the axis of the lens. Our objects are not ideal point ...
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253 views

Why do different colors appear to move at different rates when I shift my head while wearing eyeglasses?

I have significant nearsightedness (and some astigmatism), but see just fine with eyeglasses. One phenomenon I've noticed is that when I shift my head side to side or up and down while keeping my ...
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Answer different using effective focal length of combination of lens

Q)The figure shows a silvered lens. $\mu_A = 1.6$ and $\mu_B = 1.2$, $R_1 = 80$cm, $R_2 = 40$cm and $R_3 = 20$cm. An object is placed at a distance of 12 cm from this lens. Find the image position. I ...
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118 views

Spherical Lens Instead of Parabolic Lens

I know that using the paraxial approximation, spherical lenses behave like parabolic lenses. It seems that there is no reason to use spherical lenses instead of parabolic (because they are used in the ...
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60 views

What shape lens will focus parallel laser beams to the smallest point?

I'm playing with Algodoo optics. I'm trying to focus parallel lasers using refraction. I thought an ellipse or parabola would work, but not precisely. As you can see in this picture, the ellipse ...
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$ABCD$ matrix formalism for concave mirror

I need to calculate the $ABCD$ matrix for a thick concave mirror, in the situation in which the light comes from the plane side of the mirror, and it is the concave part that is coated (for reference, ...
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2k views

Relationship between the power of a convex lens and the refractive index of a medium

According to the Lensmaker's formula, $$\frac{1}{f} = (μ-1)\left(\frac{1}{R_1} - \frac{1}{R_2}\right)$$ Apparently, focal length $f$ is inversely proportional to the refractive index of the medium $μ$....
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How do the evanescent waves contribute/cause a diffraction limit?

In the following article, under the section Physics of the Superlens, it is stated: The light emitted or scattered from an object includes not only propagating waves but also evanescent waves, which ...
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99 views

Why would a 1.74 index lens be more prone to chip and be less resilient than 1.67?

My optician counselled me I don't recommend a 1.74 index with a metal grooved frame, like the one you want from ic! Berlin, because the edge will be less resilient and be more susceptible to chipping....
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How to add Aperture stop to abcd matrix?

I want to write the abcd matrix of an optical system but I am not sure how to add the aperture stop? Given the diameter of the aperture stop and the system works on f/8. With f is the f number. Any ...
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How do I find the focal point for one lens in a double lens system?

So I'm trying to construct something that will use the two lens, (1) and (2) where lens 2 is 4x bigger than lens 1. The point of this thing will be to heat the small plate at the end of the cylinder ...
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Is it possible to focus light from a screen?

Let's define a screen as a surface emitting light in all directions. What I'm trying to find out is if there is an optical method that allows bundling the emitted light to be focused on a single point ...
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74 views

Shaped charges/explosive lenses and implosion in the Fat Man design for the Nuclear Bomb: how do these actually cause implosion? [closed]

This is gone into at some length but not much detail (that I could understand) in "The Making of the Atomic Bomb" by Rhodes. The basic story is that the Americans were having trouble getting ...
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115 views

Do identical, equally spaced lenses possess the same magnification, or does it depend on the sample's distance?

Do identical, equally spaced lenses always have the same magnification, or does it depend on the sample's distance to the first lens? This question comes from trying to solve: "There are 4 ...
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Problem of lens distance - Geometrical optics

I'm study geometrical optics and I'm doing an exercise which says: To the left of a thin lens an object is located at a distance p in various positions, indicated in the table. For each of the ...

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