Optics is the study of light, and its interaction with matter. It includes topics such as imaging systems, fiber optics, lasers, quantum optics, and more.

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How can I change the divergence angle of a single mode fiber

For my project I use the end of a single mode fiber as a "transmitter". I need to set the divergence to 20 micro radians. Is there an equation how to calculate the divergence and the necessary optics ...
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2answers
71 views

How is refractive index related to the density of a medium (for example, air)?

I have a question regarding refractive index dependency on the density of a dielectric, specifically air. Background Let us start from Newton's second law form of driven harmonic oscillators ...
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1answer
31 views

What is the math behind the smartphone fish eye lenses

I found out information that these add-on fish eye lenses for smartphones have a focal length of about 2mm. I bought a lens and tried it with several different phones and it worked. I found out that ...
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1answer
25 views

Single slit diffraction - choosing a wavelength?

For the classic experiment of determining the slit width of a single slit. If we assume the rough order of magnitude of the width is known. What factors determine the choice of wavelength? (Clearly ...
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1answer
146 views

Mode groups in an optical fiber

I know what modes in an optical fiber mean but what are exactly mode groups in an optical fiber? From what I read until now, I have the impression that modes that have close propagation constants ...
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1answer
35 views

why do light bulbs explode when in contact with water?

Is it true that when water pours on a light bulb it will explode? If so does this apply to all light bulbs and how does that happen.
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45 views

Selecting an epi-illuminated objective for optical microscopy

I am currently trying to improve my silicon microphotography. To provide context: this is what I get with a 10x epi plan objective¹: This is what I get with 40x epi plan objectve with NA=0.65: I ...
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2answers
541 views

What is the difference between Sapphire and BK7?

What is the difference between Sapphire and BK7 in optics (lenses), is it only about quality?
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154 views
+50

Blue light filtering

Prologue: my knowledge in these topics is fairly limited, so please feel free to point out the mistakes or the not-so-clear points, and bear with me for the oversimplicity of the language used. I was ...
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36 views

Optical signals and the electromagnetic spectrum [on hold]

Are Optical signals are not considered part of the E-M spectrum? Or are they?
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45 views

Why does magnetic field and not electric field invert in a reflection? (related to another question)

When you are talking about an elctromagnetic wave that reflects on a surface (for example here), why do you say that the reflected magnetic field inverts and not the electric field? \begin{align} E_+ ...
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77 views

How far do we need to be removed from the earth to show the curvature with a viewing angle between 42 and 48 degrees? [duplicate]

I have seen already a couple of answers but none of them give an exact number of what should be the minimum height where we would be able to record the curvature of the earth All I could find is ...
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38 views

Determining focal length and positions of principal planes [on hold]

I have been stuck on this problem for a few days now, and I am still not confident which approach to take with this question. I am consider using the Gullstrand Equation, but I hear some of my ...
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1answer
16 views

Signal loss in non-reflected light through a tube proportional to square of the length?

Reading a patent I came across the claim: "...a portion of light intersecting the inner metal surface is not reflected, resulting in a loss in signal intensity... the signal loss is proportional to ...
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30 views

Showing the relationship between focal ratio and brightness [on hold]

I have an optics question that I have been stuck on for a few days now and I really need some guidance. Any help is appreciated! Question: The f-number (focal ratio) of a lens is the ratio of a focal ...
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1answer
25 views

Why eyepiece does not resolve image formed by objective lens further?

In my book it is written that "The angular resolution of the telescope is determined by the objective of the telescope. The stars which are not resolved in the image produced by the objective cannot ...
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0answers
18 views

DIY optical band pass filter or another alternative

I need to detect laser using a solar cell which would need me to either detect the laser wavelength or use pulse modulation and detect the frequency so I'm kinda here to ask if it's possible to simply ...
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3answers
2k views
+500

How to recover an unfocussed image

If the lenses in a camera are not set correctly, the intended subject will be "out of focus" in the resulting image. There seems to be no loss of information here. The photons are just steered to the ...
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1answer
29 views

Why rainbows form around flashes?

I read that to see a rainbow, your back must be towards the sun, and you have to look at roughly 42 Degrees from the imaginary line to spot the red band. But many times, me and many of my friends see ...
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3answers
153 views

Shining a laser onto a mirror

Theoretically, if I shined a laser at a mirror at an angle of 0 degrees so that the light was perfectly reflected back to the light source, then I should not be able to see the light because it is not ...
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1answer
39 views

Will smoke affect young's double slit experiment

If smoke is present in between the screen and slit in Young's double slit experiment using laser, will there be any change in the interference pattern? Will the fringes be obtained on the screen? ...
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1answer
357 views

Brightness of light sources

I would like to know what determines the brightness of light. I'm confused, After hours of reading, I got these definitions mixed up I need to link them together: Light intensity Brightness of ...
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2answers
47 views

Why do you need at least two rays to form an image?

Why isn't enough one light beam to form an image in your retina for example?
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3answers
3k views

Is it possible to 3D print a mirror to create a high quality telescope?

Is it possible to 3D print a mirror with todays available materials? If so, would there be a reduction in image quality?
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129 views

Why does a laser beam stay collimated?

I am looking for a simple way of explaining the collimation of a laser beam. The typical discussion of the two slit experiment of quantum theory relies heavily on the Huygens principle. Its ...
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0answers
31 views

Sign convention in geometrical optics

This is slight misconception that has bugged me. While deriving the mirror formula: $$\frac{1}{u}+\frac{1}{v}=\frac{1}{f},$$ people (as per my reference book) tend to apply the sign convention to ...
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2answers
22 views

Holography with object and reference waves with a slightly different wavelength

Recently I've been looking into holography, where one interferes the object wave with a reference wave and encodes their combined intensity on a transparency, so that if one then re illuminates the ...
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1answer
7 views

Third-order dispersion in glass, direction influence

I have learned that the third-order dispersion $\chi$ is a tensor with 81 elements. Nevertheless in glass one only has four elements, which either can be $x$ or $y$ (in this case). Now there exist ...
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14 views

Best books on wave optics for undergraduates [duplicate]

i want to know about the books that i can use for the study of wave optics
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163 views

Rule sign for concave and convex lens?

I am just totally confused about the rule sign of convex and concave lenses. The general formula: $1/v-1/u=1/f$ Is okay but when solving problem sums sometimes $v$ becomes negative sometimes $u$ and ...
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38 views

Wave vector relation in nonlinear material

A light wave ($k_1,\omega_1$) travels in a medium of refractive index $n_1$ and then encounters a nonlinear medium ($n_2$) under the angle $\theta_1$. Snell's law tells us the wave's direction in the ...
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1answer
10k views

How does a photon travel through glass?

This was discussed in an answer to a related question but I think that it deserves a separate and, hopefully, more clear answer. Consider a single photon ($\lambda$=532 nm) traveling through a plate ...
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2answers
57 views

Medium with refractive index less than unity?

What I really can't understand,What are the properties of a medium with refractive index less than unity?how does it effect light rays which fall on them?
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19 views

Temperature influence in Optical Quantum Computing

I've recently been looking into the (perhaps a bit outdated but still very interesting) field of linear optical quantum computing. Using photons as information carriers, and using objects like ...
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3answers
321 views

Why does a ray passing through optical centre remain undeviated?

How can it be explained using the laws of refraction that a light through optical centre of a lens passes undeviated? If we assume the portion of the lens in the middle to be made of even number of ...
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3answers
5k views

Focal length, power and magnification

In refracting (lens not mirror based) telescopes, to have a large magnification the objective lens needs to have a large focal length. if $\text{Power} = \frac{1}{\text{focal length}}$ then that ...
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2answers
3k views

Why do focal lengths affect magnification?

For compound lenses, the image formed by first lens acts as the imaginaryobject for the second lens. In telescopes, the objective lens projects an image on its focal point which works as the object ...
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1answer
126 views

Apparent motion in a convex mirror

Why is it that if we look at the image of a person running with a constant velocity, in a convex mirror (for instance the rear view mirror of a car), the man's velocity seems to be accelerated?
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2answers
362 views

Ideal distance of eye from a lens

I observed that when I keep constant distance between object and lens but I move my eye, I get different magnification. When I am closer to lens I can see large image of the object. But if I go away ...
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34 views
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48 views

What is the reason behind total internal reflection?

I know that when we increase i , r increases unevenly, i.e i increases a little but r increases with a greater amount. At some time, when i reaches the critical angle, r becomes 90 and if we further ...
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4answers
207 views

Infinite total internal reflection

Suppose that I have a block of some transparent material, glass, for instance, with a certain index of refraction. Suppose that the transparent material is placed in air or in any other transparent ...
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0answers
45 views

Why must this boundary condition be met? (Electromagnetic wave at interface between two mediums)

My textbook says that The laws of Electromagnetic Theory (Section 3.1) lead to certain requirements that must be met by the fields, and they are referred to as the boundary conditions. ...
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15 views

Phantom blue lights under white LED headlights?

Why do I see phantom blue lights just under (and a little to the left) of white LED headlights? They appear over where the fender is, so just a few inches below the actual lights. As the vehicle ...
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1answer
58 views

The many faces of electromagnetic waves

In my waves and optics class, we have learned several ways to treat electromagnetic waves: light rays (geometric optics), electromagnetic plane waves, spherical waves, cylindrical waves (2D). One ...
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1answer
44 views

How we are able to see red and green colored objects simultaneously if combination of red and green produces yellow?

If red and green cones in our eyes are tiggered simultaneously then our brain makes us see yellow color. But if two objects which have red and green colors respectively are placed infront of us then ...
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1answer
52 views

Is Huygens's Wave Theory still correct?

We have to study on details about Huygens's Wave Theory though we have Electromagnetic theory, quantum theory today. Is it still correct or not?
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190 views

Is near point defined for a myopic eye and far point defined for a hypermetropic eye?

I learnt about far Point of a myopic eye and near point of a hypermetropic eye. But I am confused about the above question. And if near point is defined for a myopic eye and far point defined for a ...
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1answer
18 views

Why does Diffracted Light cone diameter change in relation to angle of light beam?

I have a question about light diffraction. Take a look at these images of the Pantheon oculus. Now what I don't understand, in the first picture, the light is coming in from overhead and forms a ...
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1answer
12k views

What is the near point for the eye

So I am a teaching assistant for an introductory physics class. One of the problems on this weeks workshops is: Where is the near point (far point) of an eye for which a contact lens with power of ...