Is light a particle or a wave? – Colm Kelleher

Translator: Andrea McDonough
Reviewer: Bedirhan Cinar You look down and see a yellow pencil lying on your desk. Your eyes, and then your brain, are collecting all sorts of information about the pencil: its size, color, shape, distance, and more. But, how exactly does this happen? The ancient Greeks were the first to think more or less scientifically about what light is and how vision works. Some Greek philosophers, including Plato and Pythagoras, thought that light originated in our eyes and that vision happened when little, invisible probes were sent to gather information about far-away objects. It took over a thousand years before the Arab scientist, Alhazen, figured out that the old, Greek theory of light couldn’t be right. In Alhazen’s picture, your eyes don’t send out invisible, intelligence-gathering probes, they simply collect the light that falls into them. Alhazen’s theory accounts for a fact that the Greek’s couldn’t easily explain: why it gets dark sometimes. The idea is that very few objects actually emit their own light. The special, light-emitting objects, like the sun or a lightbulb, are known as sources of light. Most of the things we see, like that pencil on your desk, are simply reflecting light from a source rather than producing their own. So, when you look at your pencil, the light that hits your eye actually originated at the sun and has traveled millions of miles across empty space before bouncing off the pencil and into your eye, which is pretty cool when you think about it. But, what exactly is the stuff that is emitted from the sun and how do we see it? Is it a particle, like atoms, or is it a wave, like ripples on the surface of a pond? Scientists in the modern era would spend a couple of hundred years figuring out the answer to this question. Isaac Newton was one of the earliest. Newton believed that light is made up of tiny, atom-like particles, which he called corpuscles. Using this assumption, he was able to explain some properties of light. For example, refraction, which is how a beam of light appears to bend as it passes from air into water. But, in science, even geniuses sometimes get things wrong. In the 19th century, long after Newton died, scientists did a series of experiments that clearly showed that light can’t be made up of tiny, atom-like particles. For one thing, two beams of light that cross paths don’t interact with each other at all. If light were made of tiny, solid balls, then you would expect that some of the particles from Beam A would crash into some of the particles from Beam B. If that happened, the two particles involved in the collision would bounce off in random directions. But, that doesn’t happen. The beams of light pass right through each other as you can check for yourself with two laser pointers and some chalk dust. For another thing, light makes interference patterns. Interference patterns are the complicated undulations that happen when two wave patterns occupy the same space. They can be seen when two objects disturb the surface of a still pond, and also when two point-like sources of light are placed near each other. Only waves make interference patterns, particles don’t. And, as a bonus, understanding that light acts like a wave leads naturally to an explanation of what color is and why that pencil looks yellow. So, it’s settled then, light is a wave, right? Not so fast! In the 20th century, scientists did experiments that appear to show light acting like a particle. For instance, when you shine light on a metal, the light transfers its energy to the atoms in the metal in discrete packets called quanta. But, we can’t just forget about properties like interference, either. So these quanta of light aren’t at all like the tiny, hard spheres Newton imagined. This result, that light sometimes behaves like a particle and sometimes behaves like a wave, led to a revolutionary new physics theory called quantum mechanics. So, after all that, let’s go back to the question, “What is light?” Well, light isn’t really like anything we’re used to dealing with in our everyday lives. Sometimes it behaves like a particle and other times it behaves like a wave, but it isn’t exactly like either.

100 thoughts on “Is light a particle or a wave? – Colm Kelleher”

  1. When light act as particle nature, then why mass of that particles do mot increase according to mass variation of theory of relativity.?

  2. In this video:
    Exposing the Greatest Deception of all time! • The Earth is flat.

  3. Guys, what if the universe is made of some stuff like water, and everything is immersed in it, and when this stuff is disturbed, it creates waves which we call light, just like water create waves? This perfectly explains why light behaves as a particle and a wave, just like the surface of rippled water is particle and wave.

  4. 1:30 "Light […] has traveled millions of miles across empty space before bouncing off your pencil and into your eye" No wonder people have a hard time understanding quantum physics when this kind of information is regarded credible.

  5. Everything has its precise mechanism.

    Light is oscillating electrostatic force carried by vibrating matter/medium/atoms/electrons.

    Electrons are on the surface of all matters. Electrons are constantly vibrating due to the energy atom carries. The higher temperature the higher vibration frequency.

    Line of sight electrons on the sun and the moon are repelling each other constantly with the force F=Ke x ee/rr. That force is the conductor/messenger of light/radiation. That force instantaneously transfer energy between electrons on the sun and moon.

    Light speed in vacuum is infinite. Light only exist with matter/medium. Light speed in a medium is the rate of induction of electrostatic force.

    All the light and EM waves in daily life are vibrating electrostatic force moving in matter, therefore light act as wave. Photoelectric effect is misinterpretation of the vibrating force as photon particles momentum.

    There is no matter in space, no energy and wave in space, no force and field in space. Energy, force, field must co-exist with matter.

    Do a double slit experiment in vacuum, only two bright lines behind of the slits will on the screen. Measure light speed in a vacuum glass bottle using one trillion frame per second camera, you will find light speed is infinite.

  6. Aquí hay una nueva teoría sobre lo que es y no es la luz, les recomiendo estos videos

  7. I m a student in class 12 nd u explained me the whole physics chapter dual nature of radiation in just 4 min, thank u

  8. Thanks to..".de brogliee"……he concluded..that like matter light also behave as particle as well as wave nature😎😎😎thanks me later after liking comments 😂

  9. What if light is a particle that ACTS like a wave?
    That would explain why light looks like a beam ie a cylinder,because it occilates in all the directions with the same length. And the two beams not bouncing off? Well they do not collide as much because of their extreme speed of occilation and they miss. In their case of collision, there is actually light spreading in all directions just like the gold foil experiment with only one in a million that reflects back and our eyes are not sesitive enough to sense the one photon of light?
    And that's how the mafia works!

  10. Light is a field phenomenon consisting of a magnetic wave and an electric wave propagating around a radial dielectric field line and has an impulse which varies with the frequency of the wave that has been mistaken for a particle or semi-particle called a photon. Photons do not exist in reality. Just because you can count impulses does not mean they are particles. The ether was never disproven, it was simply abandoned. The so called vacuum has repeatedly been scientifically proven (by real scientists using the scientific method) to have properties of magnetic permeability and dielectric permittivity, hence cannot be the nothingness or void described by mainstream "science." Every material medium, such as air, glass, etc., has differing magnetic permeability and dielectric permittivity properties. Light does not have a constant rate of wave propagation because there is no perfectly homogeneous medium in the universe, including the ether. Any variance of the properties aforementioned will cause either an increase or a decrease in the rate of wave propagation. We do not have a way to accurately measure the rate of wave propagation of light, especially between distant objects such as the earth and the stars. The best we can do are approximations. We are currently using a circularly fallacious system in which we assume light has a constant rate of propagation, then we use that rate to calculate the distance of the stars (or whatever we are observing) and then we use that distance to verify/confirm that our rate of wave propagation is correct. All calculations are round trip as the measurements take place when the light propagates from the source and when it returns to the observers. There is no way to measure the light at the target object or during its transit to and from that object. There is quite a bit of missing information being filled purely by assumptions.

  11. It is not a particle or a wave it just acts as if it were and that way can be observed. Actually it is just a force field.

  12. here is my fringe postulate: its neither . here is what is going on . light does one thing and only one( as far as I saw) it paste it self , and the paste also paste it self and so forth , as long as there is a valid medium( from light perspective) it does this . how? the best guestimate is in the manner described by the flower of life( but I suspect its real name is flower of LIGHT .yep its way weaker then science portray it .but in my view? this is way more usefull . because light can be used via medium. yep there is no point a to point b light move . light only look to be doing that because it happen so fast ( view this week slow-mo guy video( at calltech) so what is being lazed? highest candidate in my list : plasma , radiation

  13. That's the exact reason this is called wave-particle duality. Yeah, i'm showing off as someone who learn quantum physics

  14. Light is a electromagnetic wave but if we think it in Quantum Physics light is a particle called Photon

  15. Scientists always treat particles as if they were marbles that can collide at certain times. What if this isn't the case every time?

  16. The morons at TED have no idea of the history of the world. They should not speak who did what first.

  17. At the end of the video I got an ad that was like "Accidentally using the light while taking a photo, having the screen brightness too high". Wow the coincidences. It's an Italian ad.

  18. Light is particles called photon. When the particle called photon moving at speed of light it acting exactlt as electromagnetic wave.

    In side the photon ,are the massless electric charges(one pisitive and one negative and the sum is zero) entangled together. These electric charges rotation to provide spin for the photon,allow photon has a spin equal to 1. Because one is positive and one is negative, one rotate right hand and another one rotate left hand. These counter rotating charge forming an ossilating dipole moment. And when this ossilating dipole moment moving at speed of light, it actually become electromagnetic wave.

  19. Here is my theory : Light is TWO different things observed as one À:Photons moving at c. B: Ripples in the superstrings moving at the same speed.
    As they reach the eye at the same time they are SEEN as the same thing.

  20. It's a wave it's always a wave… If it doesn't look like a wave at times it means at those times it's a wave that doesn't look like a wave.

  21. Light is a wave-particle. When you observe it light it acts like a particle, but when you don't it act like a wave. It's just how quantum reality works.

  22. If wave form is a sleeping form of energy.
    And whenever we looked at the photon represented awareness and hence acts as particle. Our thoughts and perception gives it shape. Just like what we think we become. What we feel we attract.

    And in the case, every time there was awareness/consciousness present.
    Light became particle. The medium of energy transfer.

    Just a thought

  23. You haven't answered your question.
    You said light behaves like a particle or a wave. Then what is it?.
    When you say a photon, a packets of what creature? Dark matter?.
    I believe light is a particle. For there to a wave there needs to be something. Like a photon. That's slips in the blackhole so that light will never collide.

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