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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If we increase the aperture of a telescope and decrease its magnification, can it be harmful to the eyes?

The full moon is the brightest object in the night sky. I believe that if we increase the aperture of the objective, and decrease the magnification of the telescope, it might concentrate a dangerous ...
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37 views

Optical density

My knowledge about optical density as a quantity is limited and I have several questions regarding it. I know that it is the optical density of a medium that determines the speed of light in a ...
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3answers
325 views

Does light change phase on refraction?

I have seen a lot about when light undergoes a phase change when it is reflected. But does it undergo a phase change when refracted and if so why and if not why not?
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61 views

Gaussian beam modelling, location of the beam waist?

In reference to the specifications of a laser diode below: http://www.thorlabs.de/thorcat/11900/L780P010-SpecSheet.pdf I wish to be able to model it as a gaussian laser beam. I understand there is a ...
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27 views

Transparent vs Insulator

Being transparent, can I say that glass is a better insulator than wood. (Reason: In GLASS visible light(lower energy)is not able to excite the electrons in it,so just pass away to other ...
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1answer
81 views

Total internal reflection for perpendicular incidence

Are there any materials, which give total internal reflection for perpendicular incidence? Here, by this phenomena I mean: no absorption (including for evanescent propagation inside), finite ...
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1answer
40 views

Lens surrounded by two different materials?

If have a material refractive index $n_1$ then a lens refractive index $n_2$ then another material on the other side of the lens (but in contract with the lens) refractive index $n_3$. How do I find ...
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1answer
48 views

Intensity for Single-Slit Interference Pattern

In the derivation for the equation for the relative intensity of a single-slit interference pattern in my textbook, there is an assumption that I find a bit fishy. I know this equation works, so it ...
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27 views

What property of medium is directly related to light propagation speed in that medium? [duplicate]

Refractive index is used to calculate phase velocity of light in medium, other than vacuum. Recently I had a discussion with somebody claiming that light is slower due to magnetic field of atoms. I ...
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1answer
43 views

Understanding camera lens and sensor compatibility

When a lens is specified not just by its focal length, but also the sensor format for which it is intended, what compatibility limits does that place on the sensors it can be used with? For example, ...
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22 views

Merging shadows [duplicate]

It is a strange phenomenon that when two shadows, say projected on to a wall, approach eachother (for example by moving the light sources closer), at some point the shadows seem to merge as if they ...
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4answers
67 views

Wave interference

Visualizing the double slit experiment, there are light lines and dark lines. The dark lines I understand are caused by the interference cancelling waves. What I don't understand is where the energy ...
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33 views

Diffraction of a thin mirror

I have a question about a particular case of light diffraction. A laser light collides into a "hairline" mirror (I mean a straight line mirror that halves the wavelength dimension), see the image ...
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3answers
56 views

Image angle illusion [closed]

I am not sure whether this question on-topic here. (please suggest to migrate if this is off-topic) What is the phenomenon/illusion (or something else?) known as where in a photo of a person, the ...
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1answer
130 views

Stimulated emission direction

Place a sub-micron clump of crystal violet molecules in front of a multipixel detector. Raise the molecules to an electronically excited state with a beam of 590 nm light, illuminating from the side ...
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1answer
32 views

Calculating distance between two objects viewed from an angle [closed]

I'm trying to determine the location of this vehicles rear bumper and the front edge of the white road marker. I can't tell if the vehicle is before, at the edge, or just ahead of the marker. The ...
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52 views

Gaze tracking with the pupil-glint response how does the geometry work?

I am struggling to understand the geometry behind the pupil glint response (see above) (With only one light source). I understand that you use the glint to find the corneal centre (Centre of corneal ...
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81 views

Help understanding Fizeau's calculation of speed of light

While searching for different methods of calculating Speed of light, I came across one of the methods that Fizeau discussed below which I cannot fully understand. In short, in Fizeau’s apparatus, a ...
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2answers
69 views

Penny dropped in the water: What would you see if transmitted light is parallel to the incident surface

I'm working on a problem which asks what is the greatest diameter of a paper you can use to totally shield a penny dropped in the water from view. The question claims that if the transmitted ...
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45 views

Why can't we see Rainbows from its end points? [duplicate]

We see Rainbows many times, but we always see them Horizontally or from Sideways. Why can't we see it from under it?/From the point where it starts or ends(end points)? I also want to stress on that, ...
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1answer
62 views

Why is cross section inversely proportional to wavelength for interstellar scattering?

The following problem was part of a homework for my Cosmology class: Compare the probability of interstellar scattering of photons of yellow light (5000 angstroms) and 50 micron infra-red light. ...
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1answer
71 views

Can unpolarized light be created from polarized light?

I have a question regarding this topic. According Stokes Parameters theory, unpolarized light could be described as a superposition of two independent beams of equal intensity and orthogonal ...
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1answer
48 views

Condition for formation of interference pattern

I recently came across this in a textbook of mine while studying the Young's double slit experiment. It says a condition for the formation of interference pattern is s/S < lambda/d Where s is ...
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23 views

Does dispersion take place in our eyes? [duplicate]

What do we see if a single ray of white light falls in to our eyes ? Doesn't it undergo dispersion ?
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68 views

System of Lenses. Virtual Objects and Nature of Image (Real/Virtual)

We have a certain system of lenses: Lens 1: Focal length: 19.5 cm Lens 2: Focal length : 9.5 cm I put an object 36 cm away from lens 1. Then, I put lens 2 between lens 1 and a screen. The separation ...
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1answer
233 views

Converging Lenses with Objects at “Infinity”

Whenever we take the case of an object at infinity, we say that the image formed ends up being a point of light on the focal point if we had put a screen right at the focal point. Now, for my lab, ...
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47 views

Total internal reflection angle [closed]

For what angle does total internal reflection happen? I think that it happens for angle=k*pi where k is an integer with the possible values: 0, 1, 2, 3... Is my assumption correct?
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59 views

Object inside the eye

What will be the image seen to us if an object is placed in between the focus and pole of our eye lens ? I guess no image will be formed.
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how can a lens combination take virtual object to the second lens?

When two lenses are in combination. what logic is it to take the image of first lens (which is not formed in real) as a virtual object to the second lens ?
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38 views

Ames Room, how to construct properly?

I have been assigned to create an Ame's Room for a physics project. However, the teacher told us very little about it, and wanted us to figure it out through trial and error. Today I spend 6 ...
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2answers
41 views

How to determine the difference between object distance and image distance? [closed]

How do we derrive the last equation? Whatever I tried it didn't work... Oh man I just saw, that all the did is write $b=3m-g$, how was is it possible for me to miss it...
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97 views

Geometric optics question

This question appeared on this site Q17: here A concave mirror is broken into two parts and these parts are separated by a distance if 1 cm. The focal length of the mirror is 10 cm. Find the ...
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3answers
47 views

Why we see more diverging light rays than converging light rays?

While the apparent fact that there's more diverging light rays than convergings ones seems to be intuitive, mathematically I can't find a reason to be so. More specifically, given a vector field of ...
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1answer
89 views

Diffraction and $k$-space

Regarding diffraction I am a little bit lost reading about reciprocal space and the space of $k$'s. As I understand it the Fourier relationship between a wavepacket $\Psi(\vec r,t)$ and the complex ...
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2answers
151 views

Why human and most of vertebrates cannot see Near-Infrared light (720nm-1500nm)? [closed]

On daytime, the surface of Earth is illuminated abundantly by light of spectrum from 250nm-1500nm, that includes near-ultraviolet spectrum (250nm-380nm), visible spectrum (380nm-720nm) and ...
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66 views

What is causing the separation of light in this image?

Reflection of keychain LED light on Macbook Pro (2014) screen I have also observed this phenomenon on my mobile phone and on a tablet. I assume this means it is somehow related to backlit ...
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35 views

Reason behind formation of doublets in diffraction spectrum

like if you see is Sodium (and also in Mercury), there are two discrete lines of Yellow color.. What's the reason behind formation of doublets?
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1answer
80 views

Luminance from multiple light sources

I have a LED diode: Given Luminance intensity [I] of $1.85$ cd. I want to have Luminance [B] from the light source of $75 \ {\rm cd/m^2}$. From $B=I/S$, where S is light source plane area, I get ...
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Can the granular quantum nature of light be used to engineer a maroscopic optical phenomena?

Today we have optical metamaterials and metasurfaces: materials and surfaces that are made of unit cells with an approximate size of tens of nanometers, that can that interact with light and can have ...
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1answer
78 views

Two layers of glass reflection related to wave interference [closed]

A highly reflective mirror can be made for a particular wavelength at normal incidence by using two thin layers of transparent materials of indices of refraction $n1$ and $n2 (1 < n1<n2 ) $on ...
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2answers
69 views

How to chose right lens for concentrating IR signal? [closed]

I am looking for the right acrylic lens. Since will be buying at least 1000 pieces I don't want to make any mistake. I want to concentrate the signal from IR LED in a 1cm diameter tube at one point ...
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65 views

What is the relation of scattering, extinction and absorption cross sctions with scattering parameters?

In optics and electromagnetics, they frequently calculate the extinction, scattering or absorption cross sections of a single particle (e.g. a sphere). Scattering cross section which is the ratio of ...
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24 views

What is the minimum bend radius of a square optical fiber on a microfluidic chip interface?

I want to make a microfluidic chip with colorimetry cuvettes with 100um square optical fibers coupled to the side of them. They should bend at a 90 degree angle to exit the side of the chip in a ...
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3answers
116 views

Missing factor of 1/2 in the definition of light intensity

The light field can be written as $E=A \cos\theta$ where $\theta=kz+wt$ is the phase of light wave. What we measure or see is the intensity which is the square of the light field $$I=E^2=A^2 ...
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1answer
82 views

Good resource for geometric optics

I'm looking for a good resource (preferably a book) on geometric optics. I am thorough with the basics (the mirror formula, lensmaker's formula, thin lens formula, etc). What I want is something that ...
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2answers
104 views

Describing a single photon with creation and annihilation operators

Since I am not fully aware of the creation and annihilation operator formalism for single photons, I want to ask, if the following is correct: I am considering a photon in the vacuum which travel ...
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1answer
21 views

if you're wearing goggles, will the light beam appear to travel straight?

if person A is outside a pool and person B is inside a pool with goggles, won't the light beam travel closer to the normal inside the pool but then away from the normal when it enters the goggles (due ...
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60 views

Why isn't Zemax showing a tilt on the wavefront on my telescope design?

Attached is a Zemax file Zemax File for an afocal telescope system. When i tilt the field by an angle of 2 degrees (In green) I would expect a wavefront tilt at the "Image " plane, however when I ...
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3answers
290 views

How noisy are photon detectors?

I have a single photon detector and $N$ photons per second arrive at the detector. Then something happens and the number of incoming photons per second changes by the factor of $\alpha$. So now ...
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70 views

Why does sea colour differ from place to place?

If you notice the colour of sea changes from place to place. At some places it is of blue or green and even different in beach. What must be the reason?