What exactly IS light?

Question

Hmm. All these answers are rather confusing, but I suppose one can't get more simplistic. Could you try describing it to a ninth-grade homeschooler? I haven't gotten into much of physics yet.

For any further answerers, please answer this question instead: since it's too hard to describe what light is, can you describe how it, well, lights? How do those little photon things "glow"?

Answer 1

The above answer is partially correct, but it doesn't really get at the nature of light. Light is, essentially, a time (or space) oscillating electric field. So imagine that you move your hand up and down in a pool of water, causing oscillation (a wave) in the height of the water. Light is basically the same thing, except it does not propagate in a medium (like the water does), it is simply oscillations in an electric field.

The particulate nature of light does not mean that it is just a ball flying through space, it just means that light consists of discrete packets of energy, meaning that you can't send half an oscillation, you can only send a single oscillation. There is not a very good analogue for this.

Though this is probably a fairly simplistic explanation of what light is, unless you are doing quantum electrodynamics or quantum field theory, it's generally good enough to know that 1.) light is an oscillating electric field 2.) it is quantized into packets called photons and 3.) the photons have an energy directly proportional to their wavelength/frequency.

Answer 2

The classical picture of light is a combination of oscillating electric and magnetic fields.

They oscillate in phase with each other and at right angles to each other in space. Each carries half the energy of the light wave. The wave propagates in the direction of the electric field vector 'crossed' into the magnetic field vector ('cross' refers to vector cross product).

The quantum mechanical picture still has these features but also has the idea of the photon as sort of a little 'packet' or particle of energy of an amount equal to Planck's constant h times the frequency of the light.

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I came back to read your questions about how the little photon things 'glow' -- now that's a really GREAT question! Seriously.

All our terminology will never be able to get at the heart of what you are really asking about. Now I understand finally. You want to know what makes light look lit up, right? On that one, I'm stuck.

Answer 3

Nobody knows. As David says above, 'particles' of light are called photons. But don't imagine just because you invent a fancy name that you understand what is going on.

We know that light can behave like a wave, with electric and magnetic fields, as described by Maxwell in the 1860s. We also know that light seems to behave rather like particles, as described by Einstein in 1905. That doesn't mean it is either a particle or a wave. It is more likely something really strange, which has no equivalent in the world we inhabit. To describe it as waves or photons is about as close as we can come to what it is, but really we have no idea at all.

Answer 4

Visible light consists of photons which are mass-less tiny packets of pure energy traveling (of course) at the speed of light. Visible photons are a small part of a spectrum of mass-less energy packets that includes heat rays (infrared), ultraviolet invisible rays, radio transmissions, microwaves, X-rays and gamma rays. Photons can interact with the electrons of atoms and molecules, kicking the electrons up into higher more energetic orbits and new photons are generated when electrons return to rest states in one or more steps. Photons strike the rods and cones of the eye's retina causing chemical reactions generating nerve impulses perceived as black and white impressions (rods) or colors (cones). The amount of energy carried by a photon determines its wavelength and color (as separated by a prism) and shorter wavelengths (UV, X-rays and gamma rays) are more energetic and penetrating than shorter wavelengths (infrared).

Answer 5

Light consists of photons, which are elementary particles. But they are also waves. The dual nature (wave-particle duality) of photons is one of the most sophisticated concepts in physics. Photons represent the quantum (i.e., smallest possible unit) of electromagnetic energy, but are also a particle with zero mass, enabling them to travel at the speed of light; it is impossible for any object with mass to be accelerated to that speed, because it would require an infinite amount of energy.

Answer 6

In order to answer this question, one must delve into the very creation of light at the source, the Sun generates its energy by nuclear fusion of hydrogen nuclei into helium and is in a state of hydrostatic equilibrium, neither contracting nor expanding over time. The electrons involed in this process change their energy state, and emit photons.
Hope this helps.

Answer 7

I use it to start my cigarette.