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.
Ambient for lack of a better term...
I'm reading "Beyond The Cosmic Landscape". Perhaps out of date, but a very understandable explanation of QED.
Am I right to deduce that the air which surrounds us is jam-packed with electrons emitting photons?
Thanks...
Light is Reflected from the surface of the object or pass through it(interior) and then the light is reflected ?
Sorry for my "noob" question i am a 3D designer just looking for some more knowledge
Thanks in advance
How fast would you have to go to reach a star 240 light years away in an 85-year human lifetime?
Here, I know that I'm supposed to find $v$, but I'm having a hard time setting up my equation(s) in order to reach the final answer. :(
Hi all!
In Young's double slit experiment, there are two things I cannot explain. Any help is appreciated!
The first one is why the bright fringes get dimmer as you get further from the central/brightest spot. My theory, after looking in the two books I have, is that each single slit decreases...
Hey guys
So lately, I've been interested in circuits. I am good at maths, but my physics isn't as good (hence why i signed up to ask questions). So I have a question. Imagine you have a simple circuit, like below:
Simple circuit, 1 bulb and X amount of batteries. So my question is, how many...
A quick question about this type of apparatus. The apparatus itself is composed of 2 concentric hollow cylinders. The cylinder at center is cooled below -50C. The atmosphere around the outer cylinder is at room temperature. This creates a temperature gradient in the space between the cylinders...
Hello guys , I will make this brief.Does anyone know why Semi Conductors are more sensitive to light than other materials? For example Semi Conductors are used in Photovoltaic cells.
Hello
Here is the shadow of the edge of a screen. This picture is in one of Mr Feynman's books. (Http://www.feynmanlectures.caltech.edu/I_30.html)
Of course, there is light interference in the edge of the shadow. It's normal. It's diffraction. Mr Feynman explains how to geometrically build this...
I have unpolarized light passing through a polarizator assuming the angle 0°. The polarized light then passes through two quarter-wave plates, the first one with the angle of 45° (maximum intensity) and the other one. Then it passes through a last polarizator having an orientation perpendicular...
I was reading a book called Catching the Light; a book on the history and other interesting things about light. There is a discussion in the book about refraction such as one might see when looking at a stone at the bottom of a pond when viewed at an angle. I've always just thought of the...
Special relativity requires any substance to be compressible.
Indeed, if an item were made of a perfectly rigid substance, then move one end of it, and the other end must move at the same moment - the movement must be transmitted instantly, faster than light.
Thus, the special relativity sets...
Hello,
If the speed of light is the maximum speed limit in our universe, how was the big bang event possible because surely the expansion would have been constrained by the speed of light?
Hello everyone !
At High School I have to make a little robot which is steerable with light. It has 2 photoresistors, if a photoresistor received light it switches on a motor. That allows us to go leftward or rightward. But, I have a problem. I don't manage to link every components between us...
A question about the light-waves and the double-slit experiment:
Light can be polarized: If you turn a polarization sheet in a polarized beam of light, you can see that polarized light has an angle. So the light-wave is transverse (right?)
But how does a transverse wave ‘bend’ as it goes...
Homework Statement
a) explain why a pattern of bright and dark fringes is visible on a screen when a light is shone through a double slit.
b) Use this data to determine the wavelength of light being used to create the interference pattern. Do this three different ways.
-The angle to the eighth...
This question has been bothering me for decades:
Imagine a point source in space that emits one photon per second. Would the photon expand in a globe in all directions until it strikes an object or would the photon shoot off in a random direction?
Suppose you have one target ten meters away...
Hi,
I'm doing a very simple problem, but I don't understand the diagram provided (see image below).
What is m here?
I know that m is the order with respect to the central bright fringe, but there isn't a central bright fringe (assuming those circles are the bright fringes)?
Homework...
Hello - I'm posting this here because of a discussion I got into on another forum following the recent death of Stephen Hawking. I should stress that I am by no stretch of the imagination a physicist (though I did do modules on special relativity and quantum mechanics as part of my maths degree...
Need to overlay beams by having one replacing the other where they intersect rather than have the beams be superimposed.
this is what I want: https://i.imgur.com/F6HIYBl.png
this is what I do not want: https://i.imgur.com/ylhMeEa.png
This kind of beam combining can be either achieved by the...
When the sun's rays break through a cloud there appears a radiating pattern but if one drew a line through these rays they would meet much closer than the distance to the sun. How come?
A rocket is in constant velocity. The velocity of the rocket is 150Mm/s (or 0.5 of the speed light, or 150 million meters per second) relative to us (we as observer).
We observe two lights, one moving in parallell with the rocket, another is moving in the opposite direction.
Below I have made...
In order for a conventional telescopic riflescope to function, it must invert the image two times.
As a result, the light-rays traveling through the tube must meet at two focal points.
With my limited knowledge of optics, i assume that parallell light going in through the objective will meet...
I am trying to piece together how the parabolic mirror manages to reflect the "red dot" from the focal point to the eye without distortion.
I compare this with a conventional car headlight, which operates almost exactly the same way, except it has a non-transparent backing. Why does the ret dot...
Homework Statement
Homework Equations
n1/n2 = (sinθ2)/(sinθ1) = v2/v1
The Attempt at a Solution
Moving from a lower refractive index to a higher refractive index. ( Lower density to higher density means faster speed to slower speed)
The answer is answer B, I don't understand why.
Respected physicists and members
(I am not a physicist)
I have a little doubt that i want to clarify.
If I am sitting in a stationary train, having a ball in my hand, the ball will remain stationary relative to my hand and plateform. Now if the train starts moving, again the ball is stationary...
Hi All,
Due to the differences in their conductivities, but considering that both the metallic and the glass plane surfaces produce mirror images of objects, is there any difference in the explanation of the mechanism of reflection of light in these materials?
Is it possible that the speed of light exists because we cannot move faster than our particles? I.e. the speed of electrons that create the electromagnetic force that hold matter together.
I know that Maxwell discovered that a disturbance in the electromagnetic field propagates at the speed of light - which Occam's razor would say that light being such a wave would explain it - but not definitively that that is true (e.g., gravity waves, or at least at that time in history, some...
Hello,
I came to this site, with a question in mind.
The speed of light. Nothing travels faster than the speed of light. This is a phrase, most of us are familiar with, to some extent.
The word "Nothing" has two syllables, "No" & "Thing". There is no thing, that can, travel faster than the...
Please, moderator, just delete this question if it is too silly.
I am wondering what is happening in anyone point in the SpaceTime field. That's what it is called, I think?
Because my simple understanding is that we see colours/light because of propagated electromagnetic radiation at...
Hi. Reading some recent threads I have found basic questions about light, fields, etc. For example, why something like light, associated with the electric and magnetic fields, can exist in a vacuum. And I noticed that every time I've been asked that kind of question, I answered "how" the...
Hi.
When we see a laser ray, it seems that part of the ray are brighter than the other parts and they seem like they’re vibrating and moving. It also seems there are fractures in its path. I want to know why do we see like this?
For example see this picture (it is from wikipedia). I circled...
Dear Physicists,
My understanding of physics is at the utmost basic level. Let me apologise in advance for what is probably a dumb question.
What I do know (I think):
When white light hits a prism, it comes through the other side, showing the colours of the rainbow. It is my udnerstand that...
Homework Statement
(Is the image read-able now? )
The fig 1 shows the relationship between voltage and current when voltage is applied to a certain light bulb.
Next, in fig 2, the bulb is connected in series with a 12-V battery and a 5 ohm resistor.
Question : what is the amount of power...
If you were to connect a string from one star to another (assuming everything remains still), and then you were to pull one side of the string towards you, the other would be pulled immediately, thus the "communication" between the two edges is technically faster than the speed of light? Does...
Yet the neutron degeneracy pressure is unknown correct? Said size of neutron is a variable?
What if we view the pressure as a volume knob, why could not a BH be viewed as a NS with the volume turned up from higher pressure?
The universe seems to be expanding since the farther away an object is, the faster it is moving. However, because of the finite speed of light, the farther away we look in distance, the further back in time we look. Does that mean that galaxies were moving faster in the past and are now slowing...
Homework Statement
Prove that snell's law ## {n_1}*{sin(\theta_1)} ={n_2}*{sin(\theta_2)} ## is derived from using euler-lagrange equations for the time functionals that describe the light's propagation, As described in the picture below.
Given data:
the light travels in two mediums , one is...