Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that is perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), between the infrared (with longer wavelengths) and the ultraviolet (with shorter wavelengths). This wavelength means a frequency range of roughly 430–750 terahertz (THz).
The primary properties of visible light are intensity, propagation-direction, frequency or wavelength spectrum and polarization. Its speed in a vacuum, 299 792 458 metres a second (m/s), is one of the fundamental constants of nature, as with all types of electromagnetic radiation (EMR), light is found in experimental conditions to always move at this speed in a vacuum.In physics, the term 'light' sometimes refers to electromagnetic radiation of any wavelength, whether visible or not. In this sense, gamma rays, X-rays, microwaves and radio waves are also light. Like all types of electromagnetic radiation, visible light propagates as waves. However, the energy imparted by the waves is absorbed at single locations the way particles are absorbed. The absorbed energy of the electromagnetic waves is called a photon and represents the quanta of light. When a wave of light is transformed and absorbed as a photon, the energy of the wave instantly collapses to a single location and this location is where the photon "arrives". This is what is called the wave function collapse. This dual wave-like and particle-like nature of light is known as the wave–particle duality. The study of light, known as optics, is an important research area in modern physics.
The main source of light on Earth is the Sun. Historically, another important source of light for humans has been fire, from ancient campfires to modern kerosene lamps. With the development of electric lights and power systems, electric lighting has effectively replaced firelight.
The parabolic mirror pictured below is such that all incident rays, neglecting diffraction, are reflected towards a focus.
A question states that the light cannot be focused to a point precisely, since there exists a circular diffraction pattern in the focal plane. The following diagram is...
Hi all!
Breaking down the question bit by bit:
AC is coated with a silver film which acts as a mirror - Okay, nothing as of yet right..?
A light beam is an incident onto prism at Point Q such that angle PQB is 40 degrees - This means that my incident angle is 50 degrees as shown below...
I take the following example to explain my question : when a « black-hole » is attracting a planet there is a Force which is proportional to the 2 masses and inversely proportional to the distance between the 2 masses. When the planet moves towards the « black-hole » this attraction force...
In A.P. French's Special relativity the author said,
The mass and length of the box are irrelevant here.
He said the momentum of the radiation is ##E_{radiation}/c##. We know that the momentum of a single photon with energy ##E_{photon}## is ##p_{photon}=E_{photon}/c##.
So is...
Hello,
Light, laser or not, is fundamentally electromagnetic radiation with visible wavelengths. Laser light has both high spatial coherence and temporal coherence (highly monochromatic) while regular light has both very low spatial and temporal coherence. Spatial coherence is not about spectral...
Hello to all,
In a short pulse laser emission setup, can a pulse be emmited with beam length shorter than one wavelenght? (can a pulse have a duration shorter than its period?)
Lets say a laser emmiter shoots a quarter cycle pulse, what would happen to this short beam?
(lets supose the...
Imagine that we have an electromagnetic wave or light propagating in x direction, and \mathbf{E} is oscillating in z direction and \mathbf{B} in y direction. The picture looks something like this
Now, if there exists a charged particle q on the xx axis at rest, then our B field can't do...
When we say speed of light = c m/s. Who is measuring meters and second. From SR perspective, that photon is moving towards you at speed of light so there should be time dilation, correct?
I set up the equation
.5((cos 12)^2)^x = 1/9
Solving for x gets me 34.037
34 + 1 = 35
I've entered answers of both 34 and 35 and both have been marked as wrong. Does anybody know what I'm doing wrong here?
A thin lens has an upper radius of curvature 𝑅1 and a lower radius of curvature 𝑅2. When the lens is completely surrounded by air, it has a focal distance 𝑓. The lens is then placed in the interface between air and water inside a vessel (see figure). Calculate the refractive index for the glass...
In the process of trying to understand holography I encountered a detail that I kind of knew before, but just now I realized I have no idea how it works, how is it even possible. I’m talking about a simple pinhole camera where supposedly no matter how tiny a hole is a beam of light would still...
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...
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...
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...