Tagged Questions
4
votes
2answers
191 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
40 views
Trapping EM radiation
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?
0
votes
0answers
41 views
EigenMode expansion for beam propagation
I want to understand how to apply EigenMode expansion method (http://www.photond.com/files/docs/PW03_eme_paper.pdf) for beam propagation on a system of lenses.
The interface between two mediums of ...
1
vote
1answer
84 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
149 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 ...
0
votes
0answers
216 views
What is the correct definition of “group velocity dispersion”?
When we talk about a medium with dispersion, we can define the phase velocity $v_\phi = \omega/k$ and the group velocity $v_g = d\omega/dk$. Likewise the phase index $n = c/v_\phi$ and the group index ...
4
votes
2answers
206 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 ...
1
vote
0answers
81 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
159 views
Difference in velocity of light in change in medium
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?
2
votes
3answers
495 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 ...
3
votes
2answers
68 views
limits on a gauss box of light
Consider a wall defined by $w(x,y,z) = \Theta(x-L)$ which is nonzero in the infinite semi-space of $x \ge L$, as well as a coherent planar standing EM wave travelling in the $z$ plane given by its ...
2
votes
2answers
258 views
Mean free path of UV photon
I was wondering if there's a simple way to compute the mean free path of UV photons in a optically thick medium with density n.
I've looked up at the literature ...
3
votes
2answers
92 views
Liquid crystal polarizes light reflection question
I was hoping someone could help me with understanding why a row of polarizes reflects a light wave when the whole row is the same length as the wavelength of the light.
I pretty much get the ...
4
votes
2answers
828 views
Make a semi transparent mirror with copper
The question:
How would you make a semi transparent mirror (50% reflection, 50% transmission) with glass with a layer of copper. For light $\lambda$ = 500nm Try to be as realistic as possible
What ...
3
votes
1answer
277 views
How does the grid on the microwave oven window prevent microwave radiation from coming out?
If I look through the microwave window I can see through, which means visible radiation can get out. We know also that there is a mesh on the microwave window which prevents microwave from coming out.
...
0
votes
1answer
69 views
What is the new distance for resolution of the images? [closed]
The taillights of an automobile are $1.25\:\rm{m}$ apart. Assume the pupil of a person's eye has a diameter of $5\:\rm{mm}$ and the light has an average wavelength of $604\:\rm{mm}$. At night, on a ...
2
votes
2answers
1k views
How does Newton's 2-prism experiment help to explain why light does not get dispersed into 7-colors in a parallel glass slab?
In a real parallel glass slide(with two prisms imagined to be touching each other to form a parallel glass slide),
The ray of light should pass through the Z in between without any dispersion or ...
5
votes
3answers
1k views
Can anyone explain to me why light is not dispersed into a spectrum through a parallel glass slide, but only through a prism?
The question pretty much sums up what I need to know. Why is it that light only gets dispersed into a spectrum when travelling through two non-parallel sides(like a prism) and not through something ...
1
vote
0answers
43 views
References for Radio Optics?
I'm really intrigued by a bunch of questions like 'what do radio waves look like?' 'how much RF radiation is there in the town I live in?' 'why does RF imaging work?'
But I think I need to do some ...
-2
votes
2answers
242 views
About change in velocity of a light wave as it enters a different medium [closed]
$\dfrac {sin\theta1}{sin\theta2}=\dfrac {v1}{v2}=\dfrac {n2}{n1}$
I understand this equation, but what is the velocity of a light wave going through air and what is the velocity/change in velocity as ...
1
vote
3answers
380 views
Why does change in speed of a wave make it refract?
When a light wave enters a medium with a higher refractive index (e.g. from air to standard glass) and its speed decreases, why does that make it refract/bend?
I understand that wavelength decreases ...
3
votes
2answers
673 views
Efficiencies of Coupling Light into a Fiber
I am in AMO Physics and work a lot with optics. I just wanted to get an idea of what coupling efficiencies one "should" get in a "reasonable time"* by coupling light into a fiber using different ...
3
votes
1answer
251 views
Polarization rotation: Jones Matrix that maps Horizontal to right circular
I am looking at the Poincaré sphere and I am trying to compute a Jones matrix for a particular rotation. Specifically, I would like it to perform the following maps:
$O :|H \rangle \rightarrow |R ...
0
votes
1answer
1k views
Wavelength dependent refractive index
I read in a book about optical fibers that the different spectral components of a light pulse transmitted in the fiber propagate with different velocities due to a
wavelength dependent refractive ...
2
votes
1answer
280 views
Why does the speed of light within a solid depend on frequency?
Different frequencies of light travel at different speeds through solids, which along with Snell's law allows for rainbows. Has this phenomenon of variable speeds been predicted through derivations? ...
10
votes
2answers
3k views
How do Optically Active Compounds Rotate Plane Polarized Light?
I am not sure if this is more of a Chemistry or a Physics question, but in my Organic Chem class we discussed that chiral molecules will rotate plane polarized light. However, my professor did not ...
6
votes
6answers
2k views
Why does light change direction when it travels through glass?
This was explained to me many years ago, by a physics teacher, with the following analogy:
"If someone on the beach wants to reach someone else that is in the water, they will try to travel as much ...
2
votes
0answers
118 views
Modeling a spray painted polyurethane surface reflection
I'm modeling light interaction/reflection from a fiberglass surface with polyurethane epoxy (that is very reflective) that has been spray painted with a matte black paint. I'm looking for some input ...
4
votes
1answer
1k views
Why are lasers inefficient?
Why are lasers inefficient? Is it because of the heat lost during lasing? Why couldn't there be thermocouples or turbines in parts of the cooling circuits to extract something out of that heat?
1
vote
1answer
120 views
Does a slide in a projector act as a diffuser?
I was wondering whether or not a slide in a slide projector acts as light diffuser? So when I have a light source that does not have a parallel beam on the slide can I expect that the other side of ...
-6
votes
1answer
472 views
Light Energy Absorption In Mirror
Let the amount of energy in one pulse of (laser) light be $E$, and the wavelength be $\lambda$.
This pulse goes straight to the mirror, and it is reflected by the mirror.
Let the reflectivity of ...
4
votes
2answers
749 views
What happens to light in a perfect reflective sphere?
Let's say you have the ability to shine some light into a perfectly round sphere and the sphere's interior surface was perfectly smooth and reflective and there was no way for the light to escape.
If ...
10
votes
3answers
1k views
Batman spotlight in the sky
I have noticed that obstructing a spotlight typically results in a blurred shadow unlike the crisp batman symbol in the comics of batman. Is there a way to create a spotlight with a crisp batman ...
1
vote
2answers
790 views
How do you calculate the intensity of light around the focal point from a focused collimated beam of light?
Problem/Purpose of me asking this question to you people who know more than me:
So I'm doing a science project where I'm collimating a beam of light to a focus point in a light medium (water vapor or ...
2
votes
2answers
860 views
Michelson rotating mirror experiment
Could someone explain the calculation required to answer this question. It is from a text book and the answer is recorded as 585Hz but I cannot replicate the answer.
In 1931 Michelson used a ...
2
votes
3answers
3k views
How do laser rangefinders work when the object surface is not perpendicular to the laser beam?
I find the functioning of a laser rangefinder confusing.
The explanation usually goes like this: "you shine a laser beam onto the object, the laser beam gets reflected and gets back to the device and ...
-4
votes
1answer
281 views
Light travels a straight line write down the principle in which this is manitested [closed]
Light traveles a straight line write down the principle in which this is manifested.
0
votes
4answers
825 views
How to get Intensity over a range of wavelengths from a Total Intensity
This is a theory vs experiment problem for me I think in that - as usual - I think I know the theory, but when it comes time to run an experiment, I can't actually extract squat.
So, here is my light ...
0
votes
2answers
266 views
Do and can phone signals come inside AC car which is glass-packed
Can phone signals penetrate glass, so can I expect phone signals to come if I am sitting inside a closed AC car.
Thanks,
0
votes
1answer
127 views
Merge different wavelength rays
Let's say an array of rays of light is given.
Each ray has a specific wavelength (in the range of visible light).
Example:
...
6
votes
1answer
299 views
Where does the energy go, when light is blocked by polarisation
I've been looking around about LCD monitors, and how they polarise light. When a pixel needs to be black, the light is "twisted" so that it can't go through the polarising sheet in front.
What happens ...
1
vote
0answers
341 views
Double Slit Problem, Waves and Optics [closed]
Given d(slit separation)= $0.158\:\rm{mm}$, $\lambda _{red}= 665\:\rm{nm}$, $\lambda _{g/y}= 565nm$, L(distance from screen)= $2.24\:\rm{m}$
What is the distance between the third order red and ...
2
votes
1answer
825 views
How to determine divergence of a LED source from a single biconvex lens
I'm trying to determine the divergence angle of light from a single lens that is completely illuminated by a high power LED.
Most optics textbooks only deal with imaging optics and I'm having a hard ...
14
votes
4answers
4k views
Why glass is transparent?
Once I asked this question from my teacher and he replied "because it passes light", "and why it passes light" I asked and he said "because it is transparent".
Same question again, Why glass is ...
3
votes
2answers
843 views
What is the effect of polarization on diffraction by a narrow slit?
Consider the well known demonstration of diffraction by a narrowing slit.
(See for example the demonstration at the 30 minute mark of this lecture at MIT by Walter Lewin)
It is my (possibly mistaken) ...
1
vote
5answers
3k views
13
votes
3answers
1k views
Newton's rings: What causes the other rings?
This is from an experiment we did in physics class. We shone a sodium light at a convex lens on top of a sheet of glass - and this image was captured by a USB microscope. I know what causes the main ...
2
votes
3answers
677 views
Reconciling refraction with particle theory and wave theory
I have searched the web for good answers to why refraction occurs when light moves from one medium to another with different density. I have limited background in physics and want to know if there is ...
4
votes
3answers
2k views
How can I determine transmission/reflection coefficients for light?
When light rays reflect off a boundary between two materials with different indices of refraction, a lot of the sources I've seen (recently) don't discuss the relation between the amplitude (or ...
