Tagged Questions
2
votes
0answers
29 views
What is the largest diameter an optical fiber can have? - for nonimaging visible light transmission
Is there any theoretical limitation on the size of the diameter of an Plastic optical fiber? I would like to transmit visible sunlight through it. I see bundles of small cores available but wouldn't ...
2
votes
1answer
53 views
What is the sun's spectral series?
My physics book says that six colors can be distinctly seen in white light: red, orange, yellow, green, blue, and violet. Does solar light only use these six wavelengths and mix them additively, or ...
1
vote
1answer
62 views
Factors affecting the size of a shadow
What factors affects the size of a shadow and how would you derive the diameter of a shadow of a circular object on a flat screen?
0
votes
1answer
45 views
With a box that has perfect mirrors on the inside would it be possible to trap light? [duplicate]
With a box that has many perfect relective mirrors, would it be possible to trap a beam of light in the box indefinetly?
0
votes
0answers
21 views
Specular intensity [closed]
Im currently studying for an exam and have been going through some past papers on the subject, however i have come across a question that has recursively come up each year and the notes on it are not ...
2
votes
2answers
33 views
Penetration of light in the atmosphere
While I was considering an answer to this question, I wondered how much light that enters the atmosphere reaches the ground without colliding with air molecules—if any. I've taken a good bit of ...
1
vote
2answers
100 views
Keep the light beam in a closed room, is it possible? [duplicate]
I mean if I am in a room totally closed to light. If I switch on a torch for a second then switch it off. So will the inside of room be always bright?
1
vote
2answers
52 views
Selectively visible laser beam with a controllable means
How can parts of a laser beam be made visible while others left invisible using something electronically controllable (for example, another laser beam crossing it, or a magnetic field, or heat, etc).
1
vote
2answers
214 views
Light Ray Reflection from concave mirror
Suppose a ray of light hits a concave mirror and is parallel to principle axis but far away from it such that it doesn't follow paraxial ray approximation. Will it pass through focus or between focus ...
4
votes
1answer
132 views
Young's double slit experiment viva question
My professor asked me (in my viva exam), "If, in the Fraunhofer single slit diffraction experiment, if we have 2 slits instead of one (at very short distances), What would happen?"
I answered with ...
0
votes
1answer
34 views
Can the choice of reflection angle for light can be derived from a minimality condition?
When the light hits on a surface, it reflects with the "same" angle as the one that hits the surface. I was wondering if this choice of angle can be explained by a minimality condition?
1
vote
2answers
63 views
Speed and transparency of light
I have been puzzled with a fact that as an object moves faster, it ceases its property of opacity. I mean to say that as an object moves faster we can see right through it (more clearly than in a ...
0
votes
1answer
66 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 ...
0
votes
0answers
31 views
Interference of 2 slit experiment when glass is put infront of 1 slit (+0.5 lambda optical path)
The question and answer is given in the image below:
I don't really understand how to work this out myself. How do I relate $+\frac{1}{2} \lambda$ to (phase difference) $\Delta\Phi = \pi$
UPDATE
...
1
vote
2answers
105 views
Why don't you see multiple images of an object?
Consider the ray model of light. Let's say an object such as a pencil is illuminated, and consider one point on that pencil. Since there could be many rays of light bouncing off the same point on the ...
0
votes
1answer
65 views
Which fraction of light is refracted from a source of light under a lake?
I was trying to solve this problem:
"A punctiform source of light is standing inside a lake, at a height h of the surface. f is the fraction of the total of energy emitted that escapes directly from ...
3
votes
4answers
266 views
Eye sensitivity & Danger signal
Why are danger signal in red, when the eye is most sensitive to yellow-green?
You can check luminosity function for more details...
1
vote
1answer
143 views
Is a holographic recorder able to capture a large full color picture? [closed]
Is it practical to attempt to build a 3D hologram generator that is full color and big enough to recreate a watermelon full size? If so, is real-time control feasible?
0
votes
0answers
61 views
Are EM waves scattered the most when the wavelength and the obstacle have a similar size?
I heard that when the wavelength and obstacle are similar in size, the scattering is the greatest. Is this true?
1
vote
3answers
41 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
1answer
78 views
Seeing a mirage through mirror?
Okay, I am not really good in physics (rather terrible), but nonetheless.
So, I was just wondering if you can see a mirage, is there something special in our eyes that we can see it or what? I mean, ...
1
vote
0answers
11 views
Speed of Light in a Medium [duplicate]
For light travelling in a medium with refractive index greater than one:
The "average" speed of light is slower than the speed of light in a vacuum. As far as I know, the instantaneous speed of light ...
5
votes
1answer
161 views
3D movie glasses making white light look red and blue
While waiting for a 3D movie to start, I was playing with the glasses they give you. I understand each lens has different polarized filters, so the left and right superimposed images on the screen go ...
3
votes
1answer
82 views
How would I perceive a purple ball when traveling at relativistic speeds
I have a 'thought experiment' which I'd like to ask about.
I was thinking what speed I would have to drive towards a crossing to see a red light as a green light - pretty easy, using the doppler ...
-1
votes
1answer
288 views
Focal length of Convex lens [closed]
A lens forms a real image of $3\ \text{cm}$ high of an object $1\ \text{cm}$ high. If the separation of object and image is $15\ \text{cm}$, find the focal length of the lens.
2
votes
1answer
120 views
Can light be canceled by merging with an inverted wave?
Can light waves be canceled by merging them with their inverted waves? Seems like it would violate conservation of energy but waves are added together when they overlap, right? Where is the flaw in ...
2
votes
1answer
104 views
How would one generate Brownian light? What would it look like?
When light is an equal mix of all visible frequencies, we call it white light.
By analogy, sound that is a mix of all audible frequencies is called white noise.
For sound, there is an additional ...
1
vote
1answer
457 views
Why doesn't my pinhole camera work?
We all know that light travels in straight a line, which can be proved by pinhole imaging as in the picture shown :
But when I'm doing this little experiment with an apple, no matter how I change ...
1
vote
0answers
217 views
Malus' Law (Polarization) [closed]
Consider the image below:
Let $\theta_2$ be the angle between the axes of transmission of Polarizer 2 and Polarizer 3 and $\theta_3$ be the angle between the axes of transmission of Polarizer 3 ...
3
votes
1answer
93 views
Angle of rays leaving a light source
I'm working on ray tracing and I'm trying to understand the impact of the angle at which a light-path intersects the surface of a light source on the amount of light that source delivers to the path ...
0
votes
0answers
41 views
How does a lens affect the field of view in a mirror?
If one looks into a mirror, he can see a certain field of view.
If he places a convex lens that magnifies (or a concave lens that does the opposite) in front of the mirror, but so that he can still ...
1
vote
0answers
71 views
Photon Statistics of a Coherent Gaussian Beam [closed]
Assume that a 100 pW He-Ne single-mode last emits light at 633 nm in a TEM00 Gaussian beam.
(a)What is the mean number of photons crossing a circle of radius equal to the waist radius of the beam ...
0
votes
1answer
168 views
Dispersion & Absorption in Optics
1) I understand light dispersion. But, I wonder what happens if I used a lens to focus it into a small point. Would it be a white point (would it reverse dispersion) or would I have a multicolored ...
-1
votes
1answer
80 views
Determine when a light is going into the object [closed]
Please look at this image: (http://mypages.iit.edu/~smart/acadyear/refract.gif)
How can I determine when light is going into the object?
Actually, if there is, what is the simplest way to ...
1
vote
1answer
58 views
Where do the high order rainbows appear?
This site shows locations of the high order rainbows up to sixth order. My thought is that, There should be even higher order bows like 7th, 8th, etc. (Though they would be practically impossible to ...
2
votes
0answers
87 views
Bandgap Spacing in Photonic Crystals
I am doing some self-study on photonics and have encountered the following question:
We know that amorphous electronic crystals such as amorphous silicon have a bandgap. Can amorphous photonic ...
6
votes
2answers
541 views
Why do green lasers appear brighter and stronger than red and blue lasers?
This is mostly for my own personal illumination, and isn't directly related to any school or work projects. I just picked up a trio of laser pointers (red, green, and blue), and I notice that when I ...
1
vote
1answer
77 views
Ideal four-level Gain Medium (or just any old gain medium)
What exactly is happening in a laser's gain cell when the irradiance is greater than the saturation irradiance?
Also can someone offer a clear conceptual treatment of the gain-coefficient and its ...
1
vote
1answer
47 views
Rays in Symmetric Resonator
I'm having some trouble figuring out how to get started on this question:
If I have a symmetric resonator with two concave mirrors of radii $R$ separated by a certain distance, after how many round ...
4
votes
3answers
190 views
Is the number of rays projected by a source of light finite?
Take a source of light which gives out infinite number of rays, each ray with finite number of photons and each photon with a finite amount of energy,
Then, Aren't the number of photons become ...
2
votes
1answer
142 views
Solar energy and optical fiber
I'm not really good at science or physics, just wanted to ask about the idea (doesn't have an opportunity to test this).
Will this scheme work and what can be its efficiency?(The goal is to make ...
0
votes
3answers
348 views
Liquid crystal shutter with >90% transmission?
Today's liquid crystal shutter glasses, when in the "transparent" state, exhibit only 40% light transmission.
They work using two polarizer layers, one which is liquid crystal and goes {vertical ...
0
votes
1answer
117 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 ...
0
votes
1answer
161 views
Transmission of Gaussian Beam Through Graded-Index Slab
The $ABCD$ matrix of a glass graded-index slab with refractive index $n(y)=n_0(1-\frac{1}{2}\alpha^{2}y^{2})$ and length $d$ is $A=\cos(\alpha d)$, $B=\frac{1}{\alpha}\sin(\alpha d)$, $C=-\alpha ...
2
votes
1answer
185 views
Different colors in LED/LCD display when viewed from different angle?
I want to know why different colours appear when viewed with a different angle. Can anyone tell me why?
14
votes
3answers
387 views
What are these rays that appear in photograph of sun?
In many images of light emitting objects we see such rays. Why do they appear ?
What is the math behind their number and direction?
-4
votes
1answer
70 views
Photonics: Slab As a Lens [closed]
The question can be found here: http://gyazo.com/fc4d26cd35e6ce368ad2a8ed504f1dcc
The refractive index it references can be found here: http://gyazo.com/94fd2f3b5ea7da9226c3acd56b0024c1
I'm not ...
2
votes
1answer
361 views
What are the properties of the partially polarized light on refraction?
When a ray of ordinary light is passed on the surface of the water the reflected light will be completely polarized( vibrations in one plane).
My question is what will be plane of vibration in the ...
3
votes
3answers
369 views
formula for transparency of very thin film of metal
Is there formula that gives transparency of very thin film of given metal (tens of nanometers) to the visible light/light of given wavelength ? Which properties of metals are needed for the formula ?
...
1
vote
1answer
136 views
Physics of Fireworks
This evening I saw the 4th July classic Fireworks in San Diego, and I was wondering about the most physical picture of what was happening. Does anyone have a good way to explain the detailed physical ...
