Learn About Wave Theory of Light

In summary: The double-slit experiment shows that light can behave as a wave and a particle. You can do this experiment by splitting a light beam in two, and watching how the light spreads out. If you do this experiment with different frequencies of light, you'll see that light behaves like a wave when it's a single frequency of light, and behaves like a particle when it's more than one frequency of light.
  • #1
Architeuthis Dux
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Hi, I'm new to the forums. I know next to nothing about anything related to physics.

My question is about light.

Light as a stream of particles (photons) kind of makes sense to my unscientific brain.

But light as waves?

Ocean waves are surface waves propogated across the surface of the water. Sound waves are pressure waves propogated through the air, or through whichever medium happens to be carrying the sound waves.

How can light be waves? What is the medium of propogation? How can you have waves in the empty vacuum of space? What is it that's waving?
 
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  • #2
Originally posted by Architeuthis Dux
How can light be waves? What is the medium of propogation? How can you have waves in the empty vacuum of space? What is it that's waving?
Light is believed to be wave because it behaves like a wave in familiar(to us) scales. Light is an electromagnetic wave, changing electric field produces a magnetic field and changing magnetic field produces an electric field.
Your question was in the minds of scientists from Newton to Maxwell. It was believed to propagate in a medium called "ether".
Then Michelson-Morley experiment came. Light had the same speed every direction. So there couldn't be any kind of ether.
Today, in Quantum Theory, quanta of light is photon. Photon is surely a particle (according to light amplifier experiments I think). But you know, it isn't a "particle" like a soccer ball. It is a particle that also behaves like wave. I hope this was helpful.
 
  • #3
Light is its own medium. A water wave needs a medium to propagate for the same reason that a friendship needs two people between which to exist. A water wave is a way of describing something that water does.

But we know that light is real without having something to exist within. It's not like friendship, it's like sweaters. Take away the people, you've still got sweaters. Light can propagate through air, water, plastic...or nothing at all. Here's how:

Maxwell's Equations say that magnetic fields get curly whenever there's an electric current present...or whenever there's a changing electric field. They also say that electric fields get curly whenever there's a changing magnetic field. So in the wave picture of light, here's what happens: you've got a source made of charged particles, swirling around and making electromagnetic fields. Now an electric field by itself will die off pretty fast, and so will a magnetic field by itself. But if you've got both of them together, they can work together, sort of piggy-backing off of each other's curliness. Curly E-field creates a change in the B-field, which makes it curly, to make a change in the E-field, which makes it curly... electromagnetic waves are one possible behavior for E and B-fields allowed by Maxwell's Equations, which are based on sound observations of electromagnetic phenomena. It is one of the triumphs of E&M that the predicted speed of these waves, equal to the inverse of the square root of the product of two fundamental electromagnetic constants, is exactly equal to the speed of light in a vacuum.

P
 
  • #4
Originally posted by rocketcity
A water wave needs a medium to propagate for the same reason that a friendship needs two people between which to exist. A water wave is a way of describing something that water does.

But we know that light is real without having something to exist within. It's not like friendship, it's like sweaters. Take away the people, you've still got sweaters.


That's very good. I like it.
 
  • #5
What a creativity!
 
  • #6
wave and particle?

'Light', as in electro-magentic radiation, behaves like a wave in certain experiments that you can do; for example, constructive and destructive interference (the colours on a soap film, rainbow colours from a CD in sunlight, etc).

It also behaves like a particle in other experiments, which you can also do; for example, the photoelectric effect.

How can it be both?

Here's the really fascinating thing: there's an experiment you can do which shows light behaving as both a wave and a particle! It's called the 'double-slit experiment', and is one of the easiest experiments to do, yet one of the most curious.

Once you've got your mind around that, consider this: you too have a wave nature! (So do I, Halls, kish, rocket, etc; even the Earth). Our wavelength is very small however.
 
  • #7


Originally posted by Nereid
'Light', as in electro-magentic radiation, behaves like a wave in certain experiments that you can do; for example, constructive and destructive interference (the colours on a soap film, rainbow colours from a CD in sunlight, etc).

It also behaves like a particle in other experiments, which you can also do; for example, the photoelectric effect.

How can it be both?

Here's the really fascinating thing: there's an experiment you can do which shows light behaving as both a wave and a particle! It's called the 'double-slit experiment', and is one of the easiest experiments to do, yet one of the most curious.
Wave-Particle duality is not a problem now, thanks to QED. It explains all of the wave-like behaviours of photons.

Once you've got your mind around that, consider this: you too have a wave nature! (So do I, Halls, kish, rocket, etc; even the Earth). Our wavelength is very small however.
They should have thought that Louis de Broglie was mad, but yes, that's real.
More info about nature of light: http://www.encyclopedia.com/html/section/light_thenatureoflight.asp [Broken]
 
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  • #8
kishtik wrote: Wave-Particle duality is not a problem now, thanks to QED. It explains all of the wave-like behaviours of photons.
"QED" as in "Quantum Electrodynamics".

This is something which many members of PF have asked about, and are curious about. Do you have a good, non-technical reference? One which explains QED, how it handles "wave-particle duality", and explains the wave-like behaviour of photons? The history is also fascinating; how special relativity was added to quantum mechanics, and how experiments of extraordinary accuracy have confirmed QED, to, what, 9 decimal places?

I for one would sure appreciate having such a reference to hand!
 
  • #9
The best reference is QED by Richard Feynman himself. To think and wonder and to be shocked by the nature.
 

1. What is wave theory of light?

Wave theory of light is a scientific concept that explains light as a type of electromagnetic wave. It states that light is made up of oscillating electric and magnetic fields that travel through space in a wave-like pattern.

2. Who proposed the wave theory of light?

The wave theory of light was proposed by Christiaan Huygens in the 17th century. He suggested that light was a form of wave motion and developed a mathematical theory of light based on this concept.

3. How does wave theory of light explain the properties of light?

According to wave theory of light, light exhibits properties such as diffraction, interference, and polarization. These phenomena can be explained by the wave-like behavior of light as it travels through space.

4. How does wave theory of light differ from particle theory of light?

Wave theory of light and particle theory of light are two competing theories that attempt to explain the nature of light. While wave theory focuses on light as a form of wave motion, particle theory suggests that light is made up of tiny particles called photons. Both theories have been supported by experimental evidence and are still used in different contexts.

5. What are some practical applications of wave theory of light?

Wave theory of light has many practical applications in areas such as optics, telecommunications, and imaging technology. It is the basis for understanding how lenses and mirrors work, and is also used in the development of technologies such as lasers, fiber optics, and holography.

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