Light Definition and 1000 Threads

Summary:: need to increase the wavelength of light. I am an intro physics student working on a project and need to increase the wavelength of photons. I only have visible light sources available but need to have an emission of a wavelength larger than 1mm. is there a way to shift wavelength...

In regards to human vision and specifically the retina and ganglion cells. I find it hard to comprehend that somehow the light can only hit one part of the retinal ganglion cells (either the centre or the surround) and not the other? Doesn't light go everywhere? Is the lens focusing light so...

How was it discovered that electromagnetic radiation is electromagnetic? -- Jeff, in Minneapolis

My problem started when I took my alternator apart to grease bearings when I put it back to together dash light came on so took it apart seen wire to one of the brushes was broken soldier back together it work for a short while the light was back on seen soldier had broke again so I changed...

I'm a high school teacher. In the curriculum, students are required to explain that polarization of light shows that light is a transverse wave. My answer: In order to explain polarization, we have to consider the electric field vibration direction. For example, on a wave that propagates...

I am reading up on the special theory of relativity, and watched a video. In the video we have a train moving at ½ c towards a station, where an observer is waiting. The train's headlamp is on. How would the lamp's light appear to the observer? I was thinking that it¨'d appear to the observer...

How to distinguish elliptical polarized light from partially-polarized light?

Incandescent light lamp flickering due to ? Voltage or Frequency ?

Summary: Can one observe visible light bremsstrahlung when an electron beam stops in a transparent medium? The theoretical form of a bremsstrahlung spectrum is flat at low photon energies. This means that even a high energy electron beam incident on matter should cause the emission of visible...

Summary: If the furthest quasars we can see are let's say 13 billion light years away from us, then does this mean that the distance between us and that quasar was 13 billion light years at 13 billion years ago? To anyone educated in physics this might be a silly question but to me this is...

I am not a physics guy I'm just a husband trying to read in bed at night without disturbing my wife. Does infrared light reading glasses exist?Scientificly, can they be made?

Homework Statement: Lens questions. Homework Equations: idk Hello, so I was wanting to use a laser beam and purchase a few lens' online for a project and wanted to get something similar to the image below, where i would end with a horizontal light ray i was wondering if anyone knows the...

Hello everyone, Most of you know the Holographic Sights used on weapons to aim. I have a 3d printer and I will try to replicate one of them. I just wonder how the red dot/sight is reflected on the glass without making the light reflected anywhere else? It doesn't have to have exact same...

I have unfortunately no attempt for 31.i. I don't know how to start the problem. 31.ii is attached. Can someone give me a tip on how to start 31.i? I also have troubles solving 29.iii. I have attached that as well.

In 2009, the same society together with the Tau Zero Foundation announced Project Icarus, a similar spacecraft that could achieve 15% the speed of light. That year, a physicist called Friedwardt Winterberg announced a fusion spacecraft that could be used as a capacitor to produce proton...

Let me clarify this by a thought experiment: Imagine, a heated, red-hot (emitting only monochromatic red light) metal bar is brought inside a dark room. The room is practically insulated and the metal bar is glowing in the dark - emitting 'red photons' of visible light. Eventually, the bar...

Hi I’m making a custom lamp for a Christmas present and want to create a custom on off switch to go with it. The switch part is easy, just make a mechanism that breaks or completes a circuit, but I’m not sure what to do to insure it doesn’t electrocute the user, or burst into flames. If I...

The sky is blue because the blue wavelength is rayleigh scattered. Now let's take a glass of water you use for drinking. The ordinary reasoning is that water is not rayleigh scattered. But If water were to be scattered by all wavelength. How should the water look like? I just want to have an...

The green ray is moved upwards for clarity, they are all on same x-axis with no y component. Theres a phaseshift at both reflections of the green light because n1 and n3 are > n2. This results in a complete wavelength phaseshift, aka no impact on the wave. That means that only the extra travel...

There is the famous experiment of measuring the "movement" of a star close to the sun during an eclipse. The stars position is determined before the disc of the sun moves just under it and than the position is again measured when the sun moves just "under" the star. The star will have appeared...

The wavelength of light from a moving source is red shifted which means that the wavelength has increased and the quantity of energy arriving per second at a relatively static destination is less than the quantity of energy emitted per second at the source. If so then the original quantity of...

A train is traveling around the Earth at just under light speed. Light would circle the Earth around 7 times per second so let's say this train cricles the Earth 6 times per second. There is a physical ticker on the track of the train that records revolutions. Each time the train makes one...

I have a LED light, which has a strong spectral peak around 470nm, and a broad emission spectrum in the deep red and infrared. I want to block most of the blue peak, and gold will absorb around 62% of this blue light. Will a polished gold foil surface of 1 cm2 be able to absorb 1 watt of this...

Simple as it sounds! Usually people derive aberration of light using linear motion, not circular motion. When aberration happens in linear motion, one would expect distance between the source and the observer to change. But, in circular motion, the path light takes in the circular motion, in...

Sorry if this is a stupid question but I couldn't find an answer anywhere. According to 2 scientific papers, the neutron star PSR J1748-2446ad has a rotation rate of 716Hz, which equates to a linear surface speed of 0.24c. What if this star was originally rotating, let's say, 5 times (or more)...

I know we end up with ##c=\sqrt{\frac{1}{μ _0.ε _0}}## The reason I would like a bit of help is that I understand that the value of c as deduced from Maxwell's equations is independent of any frame of reference. I can see that this is the case from the above equation involving the...

In relativity, the speed of light in vacuum is a universal constant. Also, it has wave-particle duality. So if the speed of light slows down in a different media other than vacuum, what exactly is slowing down? Macroscopically speaking, the speed of light does slow down. What about in the...

If we’re looking through a telescope at a craft we launched from Earth that is now passing Mars and send a radio signal to our craft telling it to turn on one of its lights on and it takes thirteen minutes for the radio waves to get from Earth to our craft how long will it take before we see the...

For t < 0 , all I can think of is a qualatative " the field is zero because the intensitity is 0 when the burst of light hasn't been emitted yet " For t >= 0 , I've tried squaring the given E and that let's me say the amplitudes are proportional (with a cos^2 term in the mix) But I feel like...

About a month or two ago I posted this question in the "Classical Physics" forum: if the light doesn't interact with an electromagnetic field, then which force explains light reflection in a mirror? I didn't get a clear answer for that (besides advice to buy a book from Feynmann), so I went on...

One of the emission lines of iron is 404nm, would iron absorb the heat from a blue laser and not copper? Not a student, just an old curious guy. Thanks, Philip

One of the things I have yet to come across in the explanation for the expansion of the universe is the effect of light... Most all of the matter we observe out there are stars - fusing nuclei and radiating EM energy in incomprehensible quantities... And this has been happening since the dawn...

So, pretty much I want to make an experiment in order to get the speed of light. What I plan to do is to have a lantern in the dark(initially off) perpendicular to a wall, two sensors(one closest to the lantern and the other closest to the wall), then turn on the light making sensor 1 go off as...

If I'm using the basis vectors |u> and |r> for two polarisation states which are orthogonal in state space, I've seen the representation of a general state oriented at angle theta to the horizontal written as $$\lvert\theta\rangle = \cos(\theta) \lvert r \rangle + \sin(\theta) \lvert u...

Why is speed of light in matter medium smaller than speed of light in vacuum?Are all photons must be absorbed by atoms and then the atoms re-emit radiations in matter?What is real picture of all photons in transparent medium?

So, I was in class listening to my lecturer when I notice something intriguing. I was looking at the reflection of a lamp on the screen of my calculator. I paid close attention to the colour of the light reflected of my calculator and realized that when I rotate my calculator by about 90 deg...

This is probably going to sound like a ridiculous question... but here goes. I (think) I understand that matter tells spacetime how to curve and spacetime tells matter how to move. I also know that light obeys the same laws of general relatively as matter. What I can't get my head around is...

Summary: Will the motion around us become faster when we travel faster? When we approach a body rotating on its axis with certain speed v, will we see the body rotating in speed slightly more than the v during our motion ?And what happens assuming that we are approaching the same body in speed...

One description of the interaction light with atoms states "Light waves incident on a material induce small oscillations in the atoms, causing each to radiate a small secondary wave in all directions". And another that "A photon with the right energy causes an electron to jump up to the next...

Hello! I am a bit confused about the circles of light around a black hole, that were present both in simulations and in that image of a real black hole. I understand that the gravitational field is so strong around the black hole that the light is forced to move in a circular path around (from...

I did the first three questions and found that the ignition distance without breaking would be 75 m, it would take 8.3 seconds to stop the car with a maximum acceleration of -3.0 m/s^2 and you would go 103,75 m if so.

This problem was asked in one of the most prestigious exams in India: JEE Advanced, unfortunately it was considered to be ambiguous for the scope of given examination and hence no official answer is issued for it as such.(BONUS marks to all) And so many solutions were posted on Internet which...

Light is a funny thing. If it could move slower it would have more momentum, not less! How weird is that? Or is that all wrong? I would appreciate comments on that.

Summary: I'd like to know if anyone else thinks of these things <mentor moved to general discussion>[/color] What if one day we can "warp" x light years away from Earth, build an enormous telescope, and look back at the Earth x years ago with resolution that rivals the American flag on the...

Hi, Does the distance between the light source and the slits matter? Does the interference pattern change if you move the light source closer or further from the slits? I read from this link that the collimation of the light changes with distance and that affects the interference pattern...

Hello, A light pulse moving bouncing between two mirrors (top and bottom) follows a vertical straight path w.r.t. to an inertial observer at rest relative to the mirrors. However, a moving inertial observer see the light pulse move in a zig-zag path as it bounced back and forth between the...

Hello, I have an ordinary light (not laser) collimated to produce a parallel beam. After traveling a distance in air, the beam has diverged significantly. The intensity decreases as the radial distance increases. Now I need to estimate the intensity profile along all radial distances inside the...

Homework Statement: Light with wave length 648 nm in air is incident perpendicularly from air on a film 8.76 micrometers think and with refractive index 1.35. par of the light is reflected from the first surface of the film, and part enters the film and is reflected back at the second surface...

Hello, I have a monochromatic light source (wavelength ~ 420 nm), which will be incident on the interface of two different media. Could someone please explain if the Fresnel equations applies with monochromatic light when estimating the reflectance and transmitance? Thank you in advance...

Crystal acts as a diffraction grating.Although I don't know what that means.