What is Light waves: Definition and 107 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. G

    I Standing light waves if the one-way speed of light were not constant?

    Hi. According to Wikipedia: The "one-way" speed of light, from a source to a detector, cannot be measured independently of a convention as to how to synchronize the clocks at the source and the detector. Mid 20th century, the most precise measurements of the speed of light were done using...
  2. R

    Can heavy objects be used to modulate light waves with small amplitude?

    Question: Can heavy objects be used to operate light waves with smaller amplitude, or waves with high amplitude be used to operate objects with small mass? This is a diagram I drew that illustrates my point. Heavy objects are meant to be celestial bodies, and the light source generates a beam...
  3. danielhaish

    Do two light waves with difference frequencies connect when they meet?

    for example the blue light wave have frequency of about 450Thz and the yellow wave have frequency of about 508thz (I found this data in the internet) , so if this two wave would get closer to each other we would observe them as green wave which have frequency of 526Thz . so my question is...
  4. H

    Why do higher frequency light waves bend more in a prism?

    For example, why does blue light refract more than red light in a prism?
  5. S

    Is the EM field the medium for light waves

    EM waves can propagate through empty space, but there is also the EM field. Is this field really empty space or is there something that exists that the light wave disturbs, like some kind of fluid? In areas of space where values of the field is 0, is this like empty space or more like calm...
  6. rpthomps

    Wavelength of light changing in a medium

    Good afternoon, I have read that light changes it's wavelength when it enters a different medium because it's speed changes but then I read that the speed of light doesn't change (it's always c) and it just takes longer. So, it is the "observed" wavelength that changes or some such? Any help is...
  7. R

    How do electromagnetic waves from the sun vary in wavelength?

    How does the sun emit or radiate its electromagnetic waves? https://imgur.com/odqclja Is it like the first picture where it might be spaces in between the waves or more like the picture under it where the waves are uni formally (I think is the right word) with no space in between them? Or...
  8. R

    Light waves through polarizers: transverse or longitudinal?

    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...
  9. E

    Applications of Interference of Light Waves

    Hi! I just had some questions. Is there any jobs or careers that directly relate with the interference of light waves. I know that an optical engineer would be one but they would create lenses for telescopes and stuff. I don't understand how that would relate to the interference of light, are...
  10. K

    Diffraction work differently on water waves vs light waves?

    When the water waves go through one wide slit (slit wider than wave length), there's no fringes, the water waves spread all over the sides, like in this pic: http://electron6.phys.utk.edu/light/images1-3/misc3b.jpg or in this pic...
  11. P

    Light-beam propagation across impassable barrier?

    Hi all, (See attached image file) Two mutually coherent and collimated light beams intersect as shown, creating the stationary 'bright' and 'dark' fringes of fig.A. Suppose that, after the fringe pattern has formed, we insert a very thin (compared to the fringe-width) and (ideally) perfectly...
  12. X

    Understanding the Behavior of EM Waves: A Scientist's Perspective

    Hiya, I've been reading up on EM waves and I feel I'm slowly starting to get it, but I'm not entirely sure if I do, so I was wondering if anyone could help so I can be sure I'm not making some false conclusions here. I can't seem to find any answers to the less certain parts here So as I...
  13. Arup Biswas

    Are light waves/ EM waves damped?

    We can't see objects from objects far away from us. Why? I think light waves damps! When it reaches our eyes it's amplitude is too small to be visualised! Is this true? If indeed EM waves are damped then why? If not please give a suitable definition for the mentioned phenomena too !
  14. hsdrop

    Do all light waves move at the same speed?

    I know photons all move at the speed of light and they move in a wave like pattern. So the question is. Do we take into account the up and down motion of the wave when we measure how fast it's moving or do we just measure the forward movement ?? For example, if the wave has higher and lower...
  15. DianaHerberg

    B Find 3D Models of Waves | Get Creative with 4D Displays

    I am looking for 3D (or 4D, etc.) images of waves (such as light or sound), but seem to be having difficulty locating such models. Can someone please direct me to this kind of display, or is it not something being currently done?
  16. A

    Light waves traveling through air

    Even though light is a transverse wave it travels through air . Why?
  17. N

    Radiant power of a series of light waves

    Hello everyone, I need to calculate the radiant power of an interference pattern of a series of light wave reflections. I need a value in Watts that would plug in nicely into a photodetector's responsivity function (given in Amps/Watts) and thus giving me an estimation of the output current. I...
  18. chris2112

    Light Waves on Macroscopic Scale: Distinguishing from Matter Waves?

    scientists have observed light acting as waves on a macroscopic scale before the quantum characteristics of particles were discovered. My question is what sets apart the macroscopic wavelike characteristcs of light apart from other matter waves? This may be a stupid question but can the...
  19. J

    Evanescent light waves, energy flow and tunneling

    In the full internal reflection case where we have a refracted evanescent wave, If another object is nearby, then we could have wave tunneling phenomenon(frustrated total internal reflection). 1) So, how can the evanescent wave which does not transfer any net energy produce another wave at the...
  20. S

    Light waves with 0 amplitude due to extreme red shift?

    Is it theoretically/mathematically possible for light waves to be red-shifted so much that it's amplitude is equal to zero?
  21. cainko

    MC (multiple choice) question about total internal reflection

    Homework Statement There is an optical fiber.A light ray enter it at i°.Total internal reflection occur at X. What are the necessary conditions for the light ray to travel along the core of the fiber? (I have canceled B and D already.) A.n1>n2 and angle i should be greater than a certain value...
  22. S

    What is the Wavelength of Light Used in a Double-Slit Interference Experiment?

    Upon using Thomas Young's double-slit experiment to obtain measurements, the following data were obtained. Use the data to determine the wavelength of light being used to create the interference pattern. Do this in three different ways. - The angle to the eighth maximum is 1.12 deg. - The...
  23. chris2112

    How do water waves and light waves propagate in different directions?

    I was hoping someone could explain something I'm not quite understanding about light waves. I've researched many sources but I'm still not understanding exactly how they propagate. I understand that the electric field in any perpendicular section of the light ray creates a magnetic field...
  24. M

    EM wave interacting with refelcting surface

    When trying to explain reflection through the EM treatment of light waves, how do we account for the fact that the electric/magnetic field of the incoming light would penetrate into the medium from which it is reflecting off of? Diagrams like these: show the 'reflection point' on the axis of...
  25. Robsta

    Calculate focal length of lens by diffraction.

    Homework Statement A collimated beam from a white-light source is incident normally on a transmission grating with 500 lines per mm. The transmitted light then passes through a lens which is used to project the visible (380–780 nm) spectrum of the light source on to a strip of photographic film...
  26. Aafia

    What are electromagnetic waves

    I am confusing about it that what are electromagnetic field books said that it does not require medium then how they propagate in vacuum and we also know that waves are disturbance through a medium
  27. R

    How Does an Accelerating Charge Produce Electromagnetic Pulses?

    Homework Statement This is not an assigned question, I am very confused regarding how light travels. are all of the following parts of my explanation correct? Consider a charge which undergoes an acceleration for a finite amount of time. This results in an electromagnetic pulse that propagates...
  28. J

    How Can I Measure the Width of Light Waves Using a Prism?

    I've been trying to measure the width of light waves for one of my reports but I can't seem to find where the different waves separate. now granted I'm at younger age, I just need a easier way to find out where to waves meet when you shine light through a prism onto a wall.
  29. K

    Light waves and intereference patterns

    Homework Statement [/B] You shine two flashlights on a wall. Why don’t you see an interference pattern? Homework EquationsThe Attempt at a Solution Actually, I thought you would have seen an interference pattern but if you don’t then it’s probably because the waves of light of the two...
  30. D

    Inteference of light waves distance of double&single slit

    Homework Statement in my textbook, it states that if the single slit together with the light source more closer to the double slit, the intensity of light form double slit increases . hence, the bright fringes of the inteference pattern would be brighter...i couldn't understand why . Can...
  31. D

    Inteference of incoherent light waves

    Homework Statement i know that for intefernece of light waves to occur , the light waves must be coherent. How if two light waves are incoherent? according to my notes, inteference can still occur if waves are not coherent, but the position of pattern will shift constantly with time to give...
  32. U

    WaveLengths of Light Waves and their respective photons

    Suppose you have a source of light that emits light with a wavelength of 2 meters, and you set the device to be turned on and switched off alternately. You also set it so that each interval the device is turned on is only long enough for 1 meter to be emitted (1/2 a wavelength). Do you ever...
  33. P

    Sound & Light Wave Speed & Transfer: Explained

    So, sound is a longitudinal wave, while light is a transverse wave. The speed of sound varies going from one medium to another directly proportional to the bulk modulus and inversely proportional to the density of the new medium (i.e. from air to a steel pipe). Let's say a sound wave (consisting...
  34. Q

    Light waves and their properties

    Does light intensity and brightness depend on amplitude?
  35. curious bishal

    Exploring the Different Polarization States of Light Waves

    Is light wave always linearly polarized?
  36. H

    Calculating Light's Travel Time Through Layered Media

    Homework Statement A 5.9cm-thick layer of oil (n=1.46) is sandwiched between a 1.3cm -thick sheet of glass and a 2.4cm-thick sheet of polystyrene plastic (n=1.59) How long (in ns) does it take light incident perpendicular to the glass to pass through this 9.6cm -thick sandwich...
  37. A

    Exploring the Importance of Refraction in Light Waves

    Homework Statement Why is refraction an important property of light?Homework Equations The Attempt at a Solution Refraction is turning or bending of a wave, such as light or sound, as it pass from one substance to another. So why is refraction an important property of light? Refraction is...
  38. F

    Light waves travelling in a material.

    Hi all. I am doing a project in which I have a 99%clear transparent Silicone sheet. LEDs make light pass through this material which is than picked up by phototransistors on the other side. when someone/something touches the Silicone, this deforms and the phototransistors pick up different...
  39. B

    Question about light waves canceling each other

    Hello fellow physicists :) I have the following question: take a beam of light traveling in some direction x, let's use lasers due to their coherency and monochromatic properties. Now let's take another nearly identical beam traveling in the same direction x, only that it's 180° in phase with...
  40. adjacent

    Is Light Both Waves and Particles, or Something Completely Different?

    Why do light behaves as both waves and particles?Do it behave like both at the same time or one at a time?
  41. A

    What Makes Light Waves Different from Mechanical Waves?

    i have a huge problem. the issue is " light waves are transverse waves . transverse and longitudinal are the example of mechanical waves . while light waves are not mechanical waves" can some one explain me
  42. M

    Light waves propagate with no medium

    I have come to accept that the luminiferous aether does not exist. When we say that the electromagnetic wave is an oscillation of the electromagnetic field, then is not the electromagnetic field itself a medium that permeates all space? This is probably a dumb question, but I am as dumb as...
  43. C

    Conceptual help: matter waves and light waves

    Ok so I'm coming to terms with the following: 1 - Matter is not a wave, nor does it propagate as a wave. There is no physical wave, amplitude, etc. The probability of the position of matter varies in a wave-like pattern. It is often called a wave because physicists have no explanation for why...
  44. K

    Optics question involving light waves

    I tried to solve this question. NO idea if I'm even on the right track. Homework Statement Suppose irradiation of a 100W light bubble (very small - be assumed as point source) is homogeneous in all directions. Because of low efficiency, only 2% of the electrical energy will be...
  45. E

    Frequency of Sound and Light waves

    Sorry for another dumb question. Thank you in advance. What factors effect the frequency of sound and light waves. Light waves are effected by electromagnetic energy and given by (f=E/h) right? What about sound waves? Also, to make sure, even though ultraviolet light has much more...
  46. C

    Light waves from a normal house hold globe effecting a dc circuit. Why?

    Hello. I am new to electronics and physics. Since injuring my back at work, I now have a lot of time on my hands to learn about the things that facinate me. So please forgive me for any wrong terminology or spelling and grammar mistakes. I have recently made a small jacobs ladder using a lm555...
  47. P

    Sending communications on light waves

    Here's a quick question...though it may stick on your mind for a while and become a long question. Are all light waves going to be stable for sending communications or is...this is semi rhetorical...the freqeuency of the light going to make the communication of data subject to interstellar...
  48. R

    A conceptual question about the force of light waves when reflected

    Homework Statement An EM wave with intensity=200 W/m^2 is normal to a black .2m x .3m card that absorbs 100% of the wave. (a) Find the force exerted on the card by the radiation. (b) Find the force exerted by the same wave if the card reflects 100% of the light. Homework Equations...
  49. S

    The Doppler Effect for Light Waves

    Homework Statement You are cruising to Jupiter at the posted speed limit of 0.1c when suddenly a daredevil passes you, going in the same direction, at 0.3c. At what wavelength does your rocket cruiser's light detecter "see" his red tail lights? Is this wavelength ultraviolet, visible, or...