What is Light waves: Definition and 106 Discussions

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.

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  1. J

    Angular Acceleration due to Light Waves

    Homework Statement Two square reflectors, each 1.00 cm on a side and of mass 4.00 g, are located at opposite ends of a thin, extremely light, 1.00-m rod that can rotate without friction and in a vacuum about an axle perpendicular to it through its center (the figure ). These reflectors are...
  2. B

    Light Waves, Color, and Soap Bubbles

    Homework Statement A soap bubble is floating in the air. The wall of the bubble has an index of refraction of n = 1.33. It is observed that red and violet light are reflected from the surface of the bubble, but no green light is reflected. Compute the minimum thickness of the bubble...
  3. N

    Constructive & destructive interference of light waves

    Homework Statement A glass-plate of 350 nm thickness is free standing in space. At the angle of 75 degrees, relative to the glass-plate plane, a white light point-source is placed. The diffraction (probably a typo, and should really be refraction) index of the glass is 1.33. On the same side...
  4. V

    What is Waving in Light Waves?

    This isn't homework. I just read another person's post and it jogged my head into having questions, so this is just for my curiosity. Question 1: Aside from the practical problem of finding a fuel source that travels the speed of light or faster... Why is this a fundamental rule? I really do...
  5. J

    Light waves, photons; sound waves, phonons; water waves, hydrons ?

    Light waves, photons; sound waves, phonons; water waves, "hydrons"? Light waves are made of photons; sound waves are made of phonons; so are water waves made of "hydrons", and if so, how would they behave, and would it be possible to make a water laser or something similar based on these particles.
  6. D

    The crossing of two light waves, a point standing still ?

    A light wave has mass 0, so except his movement in one direction with lightspeed C it can't be moved in an other direction. So the crossing is always the same point (don't consider that space itself is also expanding according theory). Consider you can still track the light waves after a...
  7. liometopum

    Light waves are one half kinetic and one half potential energy

    Water waves are one half kinetic energy and one half potential energy. The quote below comes from the Wikipedia wave power article. I assume that it is the same with light waves. Do people here agree? "...E is the mean wave energy density per unit horizontal area (J/m2), the sum of...
  8. P

    Do Light Waves Have Amplitude?

    Waves in general have three properties: frequency (related to wavelength), amplitude, and speed. When referring to light as a wave, it's wavelength and speed are always referenced but never its amplitude, and I was wondering if light has a fixed amplitude for all wavelengths or if it changes...
  9. R

    Phase constant for light waves

    Homework Statement We have two waves with functions: E_1 = 6 \ sin (100 \pi t) E_2 = 8 \ sin (100 \pi t + \frac{\pi}{2}) Find E_1 + E_2. Homework Equations \phi = \frac{2 \pi}{\lambda} \delta = \frac{2 \pi}{\lambda} d sin \theta \frac{\delta}{\lambda}=\frac{\phi}{2 \pi}...
  10. T

    High power lasers and nature of light waves

    I am trying to learn about high-powered lasers. i am wondering what effects the actual power of the laser (the part that makes it burn). is it wave-length or frequency. Is gamma rays more destructive then visable light, ect. Any help would be greatly appreciated
  11. T

    Doppler Effect: can light waves have different effects, depending on your speed?

    I have a question about of light waves. Moving at high speeds toward or away from visible light could be the difference of experiencing that light as violet or red. Of course this experience is due to the photoreceptors in the eye seemingly experiencing a shorter or longer wavelength. My...
  12. S

    Does expansion of spacetime also stretch amplitude of light waves?

    Expansion of spacetime stretches wavelengths and produces the red shift. Does it also stretch the amplitude of the wave, and make distant stars look brighter and therefor nearer?
  13. D

    Two Light Waves Through Plastic

    So I'm on my last try for this question, and I could really use some help, I'm completely clueless.. Two waves of light in air, of wavelength λ = 460.0 nm, are initially in phase. They then travel through plastic layers as shown in Figure 35-36, with L1 = 4.00 µm, L2 = 3.50 µm, n1 = 1.20, and...
  14. C

    How Far Is the Farther Slit from the Nearer Slit in a Double Slit Experiment?

    Homework Statement Light of wavelength 500 nm illuminates a double slit, and the interference pattern is observed on the screen. At the position of the m = 2 bright fringe, how much farther is it to the farther slit than to the nearer slit? Homework Equations \delta=...
  15. S

    Conceptual help with relativistic transformations for the energy of light waves

    I'm in a math class reading Einstein's original paper "On the Electrodynamics of Moving Bodies," from 1905. I'm stuck in Section 8, "transformation of the energy of light rays." We're basically trying to show that that Placnk's constant is Lorentz invariant- if anyone has an easy way of...
  16. D

    Why don't light waves move magnets?

    We know that light travels through the vacuum of space because it is a self perpetuating system of electronic and magnetic waves. Since this is the case, why do we not see the magnetic wave of light move magnets, or even make a magnet vibrate? Is it simply because the magnitude of the...
  17. R

    How Do You Calculate Interference Fringes in a Double Slit Experiment?

    Homework Statement A laser beam ( λ = 694 nm) is incident on two slits 0.100 mm apart. Approximately how far apart (in m) will the bright interference fringes be on the screen 5.00 m from the double slits? Homework Equations y=L\left( \frac{m \lambda}{d} \right) The Attempt at a...
  18. A

    What Causes Electrons to Emit Both Waves and Particles?

    I understand that there are multiple tests proving that electromagnetic waves carry energy through photons, but what causes the electrons to emit both waves and particles? I also don't understand how light is self propelling if anyone could explain that. I know it is related to the creation of...
  19. D

    Quantum aspect of light waves with connection with Youngs Double Slit Experiment

    So let's say for example there is a slide with two slits on it infront of a screen. A beam of electrons is aimed at it. A) What would happen to the size of the fringes on the screen if I decreased the spacing between the slits B) What would happen to the fringes if I moved the screen...
  20. F

    Why are light waves from 2 separate light bulbs incoherent?

    My notes says that this is due to how the wave patterns of both sets of light waves vary with time since the amplitudes vary due to electrons losing energy. But I don't get how this affects the coherence of both sets of light waves since they have the same frequency
  21. F

    How to derive Intensity of light waves function I/Io

    Homework Statement How do you derive the following equation given I/Io= (I/N2)[(sinNØ/2)/(sinØ/2)]2 given that Ø= (2πdsinΘ)/λ Homework Equations Ø= (2πdsinΘ)/λ d=λ/sinΘ The Attempt at a Solution I have tried substituting Ø into the equation as well as d=λ/sinΘ, but I...
  22. P

    Light waves represented by coils

    Thanks it makes a lot more sense now!
  23. C

    Three light waves combine at a point find resultant amplitude and phase angle

    Homework Statement Three light waves combine at a point where their electric field components are E1 = Eo sin \omegat E2 = Eo sin (\omegat - 2\pi/3) E3 = Eo sin (\omegat + \pi/3) Find the resultant amplitude of the electric field ER at that point and it's phase angle\beta Write...
  24. C

    Calculate the frequency, energy, and number of photons emitted by a DVD player's laser?

    Homework Statement The laser used in a typical DVD player has a wavelength λ = 650 nm and power of 240 mW. (a) Look up the speed of light in empty space and calculate the frequency f of this laser light. (b) Light of f carries energy in bundles of hf, called “photons”, where h is Planck’s...
  25. W

    Does Coherent Light Waves Frequency Matter?

    does coherent LIGHT waves with a constant phase difference MUST have the same frequency? what about LIGHT waves with the same frequency only? will it be not coherent??
  26. G

    Coherent Light Waves: Interference & Diffraction Explained

    So is this the ability for light waves to add up and subtract interms of interference? But I am confused as to what a non-coherent light sorce would be. I mean is it when the light waves are not organised enough? So there is no effect of interference through diffraction? or is it that there is...
  27. U

    Sending information on light waves

    just likes radios and such. i had a brief discussion with my math teacher on the subject, my math teacher was an electonical engineer at Bell Laboratories for 10 years, and i asked if its possible with radio, can't it be done with any light? He said yes. what i didnt ask him was, how exactly it...
  28. X

    Do light waves change over distance within a vacuum?

    Specifically, does the amplitude of a wave of light change if it does not encounter any matter?
  29. M

    Why Are Visible Light Waves So Puny?

    This is purely a question I know little or nothing about light and the whole EM spectrum for that matter I was just wondering something. Why are visible light waves so puny compared to other frequencies on the EM spectrum. What I mean is that I can send a pulse to an antenna and emit let's say...
  30. S

    Destructive Interference of Light Waves in Bubble Film (165 nm)

    Ok so I've been thinking this problem over and over and I understand the problem and its concept but I just don't know where to start and how to do this, someone please guide me through this Light waves of which wavelength will destructively interfere due to the thickness of the bubble film...
  31. M

    Light waves through grating. Min and Max measurements of wavelenghts in nm

    Homework Statement Light passes through a 220 lines/mm grating and is observed on a 1.4m wide screen located 1.2m behind the grating. Three bright fringes are seen on both sides of the central maximum. What are the minimum and maximum possible values of the wavelength? Express your answers in...
  32. edguy99

    Can light waves be represented as long skinny rays in computer programming?

    I am a computer programmer attempting to represent light rays traveling through the air, bumping into things, reflecting and refracting in some manner as they go through glass or other material. I have had good luck and the pictures look quite nice representing light photons as long skinny...
  33. M

    Good resource for understanding light waves?

    In a general physics class, one of the things we are studying is light waves. Optics is my biggest struggle within physics anyway, and now my book is explaining what happens when a laser is pointed through a barrier with holes on it. It includes some trigonometric formulas for...I don't even...
  34. J

    Comparing Radio and Light Waves: Is EM Radiation Misleading?

    As I've been studying up on EM radiation, I've come to the conclusion that radio and light waves are not the same thing. Radio seems to be nothing other than a continuously flipping magnetic field (source: http://www.pbs.org/wgbh/aso/tryit/radio/radiowaves.html). In this way, there do not seem...
  35. C

    What Happens to Light Waves When They Move Between Different Refractive Indices?

    As a light wave enters from a material of lower refractive index (air, say) to a material of higher refractive index (glass, for example), the speed of the wave and its wavelength both decrease. Let's say a light wave enters a pane of glass and then exits the other side of the glass, back...
  36. L

    Light waves vs. mechanical waves

    Homework Statement I just have a question; what's the main difference between light waves and mechanical waves? I know that light waves are transverse. I also know that water waves are transverse, but sound waves are longitudinal. I know that light has a dual nature, and travels in both wave...
  37. J

    Light Waves at Edge of Universe Question

    Since the outer boundry(s) of our expanding universe are moving at a less than the speed of light rate there must be light waves generated in our universe that travel to the limits of our expanding universe and reach the "edge" of it. What takes place when they reach this edge? Can they "bust...
  38. A

    Question about light waves and phases.

    I am a sound tech and I no from my work there that if you have (in theory) two sound waves and 1 is 180 degrees out of phase with the other that they will cancel each other out. - This is mainly the basic theory of noise canceling headphones (along with some acoustic material, etc) and balanced...
  39. L

    What is the minimum thickness of a thin film for maximum light reflection?

    1984 PHYSICS B WAVES The surface of a glass plate (index of refraction n3 = 1.50) is coated with a transparent thin film (index of refraction n2 = 1.25). A beam of monochromatic light of wavelength 6.0 X 10-7 meter traveling in air (index of refraction n1 = 1.00) is incident normally on...
  40. D

    Doppler Effect of Light Waves at Half Speed?

    I cannot search the forum to check if this has been posted before, because I do not know what it is called in english... That means that i have to try to explain what i means, here it goes: When a light producer, like a star is moving, it sends out waves that is either compressed or expanded...
  41. R

    What Do Light Waves Travel Through?

    sound waves travel through air; waves on the sea travel through water; what do light waves travel through?
  42. A

    Light Waves & Double-Slit Experiment Question .

    Light Waves & Double-Slit Experiment Question... Our professor gave us an extra credit question on our last quiz & every single student got it wrong, all 150 of us! Anyways, here is the question, if you know the answer that would be greatly appreciated. Here is the question: Describe in as...
  43. D

    Exploring Alternative Ways to Cool Electronics: Light Waves?

    There must be another way to remove heat from electronic equipment rather than passing cool air over the surface? What about light waves? Can they cool a surface? Can they absorb heat, reflect away heat? Any one have any lateral thoughts?
  44. D

    Understanding the Role of 'y' in Interference of Light Waves Equations

    Equations dealing with the interference of light waves have a variable 'delta y'. My biggest problem is understanding what 'y' represents? Does it define the distance between two adjacent fringes? Or the distance of a fringe from the origin? this scepticism might have been the reason for my...
  45. I

    Questions about Young's Double-Slit experiment and light waves intereference

    Hello. I just have some questions about Young's Double-Slit experiment and light wave interference. I think i got the right answers, but i just want to know if i grasped the concept correctly. 1-If we perform young's double slit experiment under water, how would the interference pattern be...
  46. W

    Is it the meadiem Light waves effect?

    I heard about this from my teacher. What is it? Is it real? Is it the meadiem Light waves effect? Any help accepted.
  47. R

    Sound vs Light Waves: Compare & Contrast

    Dear friends, What are de principal differences between sound and light waves?
  48. R

    Is the Group Velocity of Light Always Equal to c?

    Dear Friends and Phorum, I need to know how to calculate the group velocity of light. I've read that's exactly "c", but I don't know how to calculate it.
  49. T

    Constant frequency for light waves?

    "what is the frequency of red light in the air? What is the frequency of red light in the glass?" is the frequency of a light wave length constant? therefore, the answer would be the same?
  50. T

    Exploring Light Waves: What is the Medium?

    new to the forums, had a question and thought someone might have an answer. If I remember from high school physics, in order for a wave to occur it must pass through a medium i.e.. sound through air, waves through water. my question is what do light waves use as there medium as they can travel...
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