-2
votes
0answers
49 views
0
votes
0answers
20 views

Refractive index variation with colors [duplicate]

To explain the spectrum formation in the prism, my teacher said that different colors have different speeds in a medium, so, refractive index is different for all. So, angle is different. But I don't ...
2
votes
1answer
53 views

Why does the speed of the Electromagnetic wave in the material depend on the frequency of the wave where as they are constant in vacuum (freespace)? [duplicate]

I am confused on why would the propagation speed of any EM waves at ANY frequency is constant in the free space (vacuum) but they seem to disperse in any other materials as the propagation speed of EM ...
12
votes
1answer
474 views

Why is Huygens' principle only valid in an odd number of spatial dimensions?

Apparently Huygens' principle is only valid in an odd number of spatial dimensions: http://mathoverflow.net/a/5396/21349 Huygen's principle in curved spacetimes Why is this? [EDIT] This is ...
1
vote
2answers
33 views

optical diffusion (scattering) versus refraction

When an electromagnetic wave meets an interface a part of it is reflected and part of it is refracted (and from the refractive index I can calculate the angles of propagation and the intensities using ...
11
votes
4answers
223 views

Does the speed of medium affect the path of light?

Let's say I shine a laser from a stationary medium into a moving medium (suppose the water is moving very quickly) perpendicular to the interface and back to a stationary medium like this: (Note: ...
4
votes
2answers
142 views

Is a Perfect/Lossless Mirror possible?

In traditional mirrors, some of the input light is absorbed by atoms in the mirrors surface and are 'lost' as heat, degrading the quality of the reflected image. Could this loss be compensated by an ...
0
votes
3answers
119 views

Duality behavior of light and effect of system scale on its behavior [closed]

Does an electromagnetic wave that makes by antenna behaves purely as wave for all the times? or it can change its behavior as photon? and does the scale of system effect on behaving as EM wave or ...
8
votes
3answers
537 views

Why use lasers for intense, localized heat instead of some other light source?

Lasers are used in various industrial processes that need intense, localised, heat (3d printers and laser cutters come to mind). My question is: why use lasers? There are many other (cheaper, ...
6
votes
1answer
216 views

The skin effect and the reflectivity of gold

I am simulating a waveguide in COMSOL, a FEM solver. My model looks like this (it is similar to a standard Quantum Cascade Laser geometry): Therefore there is a very thin (30nm) layer of gold ...
5
votes
4answers
181 views

Question about the wave nature of light

I quote from my textbook, " Consider two vertical slits S1 and S2 placed parallel to each other, and a string is passed through them. The end B is fixed and A is given jerks perpendicular to its ...
1
vote
1answer
25 views

What is the difference in application for near infrared camera data capture as opposed to infrared data capture?

I am trying to understand why I would use a near infrared as opposed to an infrared camera for data capture of vegetation health monitoring.
1
vote
1answer
157 views

How to calculate loss due to Gaussian beam divergence of a laser going through multiple lenses?

To better explain my question, I will need to give a brief description of the configuration used in 2D MEMS switches. So, the next figure shows a configuration of a 2D MEMS switch, a light beam ...
5
votes
2answers
162 views

Is my simulation result for unpolarized light correct?

This is a follow-up of this question. After that, I picked up some knowledge of FDTD (an algorithm for solving Maxwell's equations) and simulated following scene: Pic 1 As the picture shows, a ...
0
votes
2answers
416 views

Why does the light travel slower in denser medium? [duplicate]

Wikipedia says that "in general, the refractive index of a glass increases with its density." And the refraction index of water vapor is less than ice, and even less than liquid water. Is there any ...
0
votes
0answers
36 views

Would electron degenerate matter be a good x-ray reflector?

I do not know much about x-ray physics or degenerate matter, but I have the intuitive feeling that the high electron density and what must be some crazy band structures in electron degenerate matter ...
1
vote
1answer
89 views

Deriving and gaining intuition for the equation for the index of refraction $n = \sqrt{\mu_r\epsilon_r}$

I've come across the equation in the title. It relates the index of refraction of a substance to the square root of the product of the relative permittivity and the relative permeability at whatever ...
1
vote
1answer
107 views

What really is reflection? [duplicate]

What really is reflection? Is it just the reemission of EMR? I asked my teacher, he said in quantum sense, it is true. But when I read something about emissivity in Stefan Boltzmann's equation, it ...
1
vote
1answer
61 views

Characteristic quantities in Fiber optics

I'm having trouble finding typical quantities in fiber optic communication. In particular, what kind of powers are generally used (or what is the minimum that fiber optics receivers can detect ...
0
votes
0answers
52 views

Spatial light modulation for mode multiplexing, how does it work?

If a laser light becomes spatial phase modulated (by phase only spatial light modulator) what happens to the intensity distribution and frequency spectrum of the laser light ? I know that this ...
1
vote
2answers
95 views

Do acousto-optic modulators shift the frequency of the diffracted beams?

Today I read an introduction on an optical device called an acousto-optic modulator, which is used in many optical experiments. It is the first time I have heard of this element. The material showed ...
2
votes
1answer
65 views

Why electric field has a major role in vision?

Although the electromagnetic wave is made op of both electric and magnetic fields the electric field contributes much in vision and is thus, called the light vector. But, why is it that the electric ...
1
vote
2answers
262 views

A difference between Plane Wave and Collimated?

Collimation is clearly in reference to ray($\vec{k}_{xy}$ vector) orientation unlike waterfront continuity( $\phi_{xy}$ phase shift) described by plane-wave. Not to say that one is not directly ...
1
vote
2answers
416 views

Exciting Surface Plasmon-Polaritons with Grating Coupling

I'm very new the topic of SPPs and have been trying to understand this particular method of exciting surface plasmons using a 1D periodic grating of grooves, with distance $a$ between each groove. If ...
3
votes
1answer
71 views

Michelson interferogram white light pattern symmetry

Why is the white light of the interferogram produced by using Michelson Interferometer necessarily symmetric? This is really hard to think.
3
votes
3answers
210 views

What electric field vector should I use for modeling unpolarized light?

Regardless of computational cost, light is a kind of electromagnetic wave, so it can be simulated with Maxwell's equations. If we want to simulate light with Maxwell's equations, we need to express ...
1
vote
1answer
204 views

Explanation of photon reflection [duplicate]

What occurs in atomic scale that cause the photon to be reflected? In other words, what is the reason for photons to change its direction and why material can reflect certain wavelengths and absorb ...
2
votes
2answers
79 views

Are there any known, non-spectroscopic effects of EM directly on Light?

Photons have no charge. Light is a form of electromagnetic energy. All spectroscopic effects (to my knowledge) are due to changes in electron state, induced either through an interior or exterior EM ...
10
votes
3answers
524 views

What causes atoms to have their specific colors?

I understand that light (color) is part of the electromagnetic spectrum, and that it depends on what wavelengths are reflected/absorbed. Though what property of an individual atom gives it its color? ...
5
votes
1answer
193 views

Why Negative refractive index is negative

$n=\sqrt{\epsilon \mu }$ Negative refractive index happens when permittivity ($\epsilon $) and permeability ($\mu $)of a material is negative. My question is, if permittivity and permeabilitity of a ...
3
votes
1answer
63 views

How far can diffused undersea light travel and still be perceived by the human eye?

Example: If one SCUBA diver looks past another SCUBA diver horizontally into negative space, how far away is the most distant emission of 'blue' light waves? Consider the sight angle in question to ...
0
votes
0answers
42 views

Why is a $\pi$ phase added on reflection and why do things change with absorption? [duplicate]

Mathematically, how does a $\pi$ phase shift appear upon reflection of light off a optically denser medium? Why is it always $\pi$? If the medium is absorptive it is no longer $\pi$?
1
vote
2answers
206 views

Calculate the polarization vector on reflection or refraction from a dielectric interface

I am interested in ray-tracing polarized photons. I have code that works very well for unpolarized light. When a ray hits a dielectric interface the photon is either reflected or refracted by ...
2
votes
1answer
104 views

Energy conservation in plane wave

In plane wave the H and E are in phase. So the pointing vector disappears regularly every pi. How is energy conservation validated ? Is it through the uncertainty of energy and time ?
4
votes
1answer
146 views

Light entering in a 0° angle, is there any reflection?

Is there any reflection of light that enters a new medium at a 0° angle, if the electric field is such, that it is completely in the plane of the double layer?
2
votes
1answer
90 views

Cross-section of a wave packet

In text books, wave packets are one-dimensional drawings. But we live in a three-dimensional world. Suppose a wave packet from a HI-cloud (frequency 1420 MHz) is approaching the earth, distance about ...
2
votes
1answer
57 views

How does an optic-mechanical laser read and send binary bytes to a CPU?

Thid greatly concerns physics, since a more refined version of my title will be rehearsed below: How is the physical structure of the mechanical eye use a laser to read binary bits held on an optical ...
6
votes
2answers
266 views

polarization of the lower mode gaussian beam

In most introductory analysis of Gaussian beam optics, Helmoltz scalar optics is assumed. Hence polarisation is ignored. But I'm not clear what are the possible orientations for the lower transverse ...
1
vote
1answer
218 views

Simple Question: Speed of Electromagnetic Waves in a Medium

If the speed of an electromagnetic wave in a particular medium is such that $v = c$, the speed of light, does this mean that the permeability $\mu = \mu_0$, i.e. that of a vacuum and the index of ...
2
votes
1answer
223 views

How to calculate beam spread of a non-point light source via an aspheric lens

I need to determine the angle, or rate of divergence of light from a single aspheric lens when I place a non-point light source (e.g. LED array) at a given distance from the lens which is less than ...
5
votes
2answers
286 views

How do you calculate power at the focal point of a mirror?

I'm a Mechanical Engineering student and I'm working on my senior project, so I need help. My project is about designing a solar dish having a diameter of 1.5 meters and a focal length of 60cm. so at ...
1
vote
3answers
81 views

Trapping EM radiation [duplicate]

Is there a material which can allow light (or any other EM radiation) to pass through from one side as if it is transparent but its other side reflects light like a mirror?
1
vote
1answer
276 views

Eikonal approximation for wave optics. Why follow the unit vector parallel to the Pointing vector?

The description of the passage from wave optics to geometrical optics claims that light rays are the integral curves of a certain vector field (the Pointing vector direction, normalized to 1). Here ...
3
votes
1answer
303 views

Computer-Generated Holograms: I'm completely lost. How are they physically implemented?

I have been reading about holography, and I think I understand the general concept, but one thing that has me completely lost is how computer generated holography works in practice. I think I get the ...
5
votes
2answers
475 views

Jones vector and matrices

With Jones vectors and matrices one can describe the change in polarization of a EM wave. What is the convention of the reference coordinate system; Is it fixed or does it change whenever the ...
2
votes
0answers
211 views

How to calculate radiative transition rate of exciton in a quantum dot with specific dimension?

I am writing rate equations for a nanophotonic system including three quantum dots. I need to calculate that radiative transition rates of exciton in ground state in those quantum dots. In the paper ...
2
votes
3answers
420 views

Difference in velocity of light in change in medium [duplicate]

It is often seen that according to physics the light changes it's velocity according to the medium through which it is traveling. So can it be explained that why so happen?
-1
votes
4answers
112 views

What kind of “camera” and “light” source should I use to detect the intermediate path of a light beam? [closed]

I would like to have an image (in any kind of space), where I see the path of a "light" source. In my understanding the most common, directed source would be a laser pointer. a) Is this correct? If ...
0
votes
1answer
239 views

Width of Gaussian Beam and Refractive Index

I know that in free space, the width of a Gaussian beam can be written as $W=W_0\sqrt{1+(\frac{z}{z_0})^{2}}$. However, I was wondering if it was possible to express this width as a function of ...
2
votes
3answers
2k views

Reflection of Electromagnetic Waves

Visible light - Being an Electromagnetic wave is reflected by glass (take mirror). Would all other waves in the electromagnetic spectrum be reflected in the same way by our simple mirror... For highly ...