Understanding Light in Layman's terms

[Landon Caeli]

I've been independently researching the subject of light, and my understanding is that what we call "light" is our perception of a phenomenon in nature that consists of both photons and waves simultaneously, and with being two things at the same time, light is studied in two different ways, using two different fields of study... Interesting as that is.

But my question here revolves more around the wave aspect of light, and my question is about where the wave frequency originates, and the cause of the frequency.

*disclaimer*
As a thread rule, let's maintain the forum vision found in the Terms of Service and Christian Forum Rules | Christian Forums, and maintain a level of respect for each other, regardless of our level of scientific understandings, and reject, together, the use of overly provocative posts, that might otherwise cause disruption, or annoyances, or posts which personally attack other members out of anger and frustration, like we see all too often in science discussions.

Now for something to help stimulate our creative-thinking side.

 

[Ophiolite]

But my question here revolves more around the wave aspect of light, and my question is about where the wave frequency originates, and the cause of the frequency.

My understanding, which is that of a simple-minded geologist, is that the frequency is dependent upon the energy level difference between electron orbitals, when a photon is emitted as an elctron drops from one level to a lower one. I presume you are looking for something deeper than that, yes?

 

[Landon Caeli]

My understanding, which is that of a simple-minded geologist, is that the frequency is dependent upon the energy level difference between electron orbitals, when a photon is emitted as an elctron drops from one level to a lower one. I presume you are looking for something deeper than that, yes?

That is interesting and useful. But I wonder if the sun produces different wavelengths than a light bulb. I'm assuming it does not. And so I'm wondering why these two sources of light, being so different, produce similar wave frequencies.

Perhaps all light sources, produce all the wavelengths all the time?

 

[Ophiolite]

That is interesting and useful. But I wonder if the sun produces different wavelengths than a light bulb. I'm assuming it does not. And so I'm wondering why these two sources of light, being so different, produce similar wave frequencies.

The transitions from one energy level to another are similar across the elements, so it is to be expected. However, the sun produces a wider range of wavelengths than a light bulb. That's not surprising since the the function of the light bulb is - clue in the name - to produce light, whereas the sun produces across more of the electromagnetic spectrum.

Recall that it is the dark absorbtion lines in the spectrum that let us identify specific elements in the sun (and other stars) by relating them to transitions measured in the laboratory. On a historical note, helium was identified in the sun before its discovery on the Earth via the spectrum.

Landon - you'll get a much better read on this via wikipedia or similar, than from my simplistic (and perhaps erroneous) explanation based upon half century old recollectionsof school science class.

 

[Landon Caeli]

The transitions from one energy level to another are similar across the elements, so it is to be expected. However, the sun produces a wider range of wavelengths than a light bulb. That's not surprising since the the function of the light bulb is - clue in the name - to produce light, whereas the sun produces across more of the electromagnetic spectrum.

Recall that it is the dark absorbtion lines in the spectrum that let us identify specific elements in the sun (and other stars) by relating them to transitions measured in the laboratory. On a historical note, helium was identified in the sun before its discovery on the Earth via the spectrum.

Landon - you'll get a much better read on this via wikipedia or similar, than from my simplistic (and perhaps erroneous) explanation based upon half century old recollectionsof school science class.

It's just that I learn better interactively than with blocks of texts. My only goal to learn as much as I can, with paying as little money as possible, and forums seem to be one path that works well for me.

But I do appreciate what you do here!

 

[Trusting in Him]

Back in the late sixties and early seventies. I worked in the design labs of a radio and television company. White ligh as displayed on a colour television screen had to be compliant with a particular standard "colour temperature", this particular colour temperature was referred to as "illumiinant D". This colour of this particular white illumination needed to by measured in a darkened room.

It was a very long time ago and I can't remember much about it now, but there are different colours of white light. Cold colours contain more blue light, while warmer colours contain more red light. If you go to buy a domestic light bulb for your house, some bulbs will be specified according to the colour temperature of the white light which the light bulb produces.

Different bulbs are classified as "warm white", soft white" and names like that. I'm not really all that knowledgable on this particular subject, but some forum members may have a more specific understanding about this, than myself. However in essence, befining what colour is white light, or what colour white a surface is, is far from simple if you ask those who understand the subject.

 

[Landon Caeli]

Back in the late sixties and early seventies. I worked in the design labs of a radio and television company. White ligh as displayed on a colour television screen had to be compliant with a particular standard "colour temperature", this particular colour temperature was referred to as "illumiinant D". This colour of this particular white illumination needed to by measured in a darkened room.

It was a very long time ago and I can't remember much about it now, but there are different colours of white light. Cold colours contain more blue light, while warmer colours contain more red light. If you go to buy a domestic light bulb for your house, some bulbs will be specified according to the colour temperature of the white light which the light bulb produces.

Different bulbs are classified as "warm white", soft white" and names like that. I'm not really all that knowledgable on this particular subject, but some forum members may have a more specific understanding about this, than myself. However in essence, befining what colour is white light, or what colour white a surface is, is far from simple if you ask those who understand the subject.

That is extremely interesting to me. Thanks.

 

[sjastro]

That is interesting and useful. But I wonder if the sun produces different wavelengths than a light bulb. I'm assuming it does not. And so I'm wondering why these two sources of light, being so different, produce similar wave frequencies.

Perhaps all light sources, produce all the wavelengths all the time?

The Sun is a (non ideal) blackbody.

It's from the study of blackbody radiation which led to a major crisis in physics in the early 20th century known as the "ultraviolet catastrophe" and was resolved by the idea light is composed of packets of energy or photons.
This lead to the development of quantum mechanics.

 

[LeafByNiggle]

That is interesting and useful. But I wonder if the sun produces different wavelengths than a light bulb. I'm assuming it does not. And so I'm wondering why these two sources of light, being so different, produce similar wave frequencies.

Perhaps all light sources, produce all the wavelengths all the time?

The wavelengths of light from most sources form a spectrum of frequencies, not just a single frequency. It may be helpful to use sound as an analogy because our senses are better equipped to register and understand individual frequencies of sound than they are to register individual frequencies of light.

White light, from either the sun or from a light bulb, is analogous to a cacophony of sounds that you might hear in the roar of the crowd at a football game. It has no one single frequency, but a combination of an infinite number of frequencies. Red light, such as you might see from an incandescent red tinted light bulb is something like the crowd at a sporting event as they sing the last note in the National Anthem. They are all trying (with varying degrees of success) to hit one note. There is a spread of frequencies, but most of them cluster around one central note. A red laser light on the other hand is more like a really good flute player holding one single note very steady with no vibrato. That is what is called "coherent" light.

Then there is light beyond what you can see. Infrared light (which is also emitted from both the sun and a light bulb) is like a 64-foot organ pipe producing a pitch so low that we can only feel it, not really hear it. Ultra violet light (which is omitted from the sun, but not from ordinary light bulbs) is like a dog whistle, or the sound made by bats. It is way too high to hear.

Light sources are sometimes rated according to their "color temperature" which is roughly the color that would be emitted by a black body (that's an object that does not reflect any light, and so appears perfectly black) when that body is heated to that temperature. Even though a black body does not reflect any light, it does glow when heated high enough. Color temperature affects photography as photos taken in direct sunlight have more blue light while photos taken with incandescent light have more red light. The sun has a higher color temperature than an incandescent light bulb. Fluorescent lights tend to be higher color temperature, more like the sun, but the spectrum is not as filled out as sunlight. LED lights can be made to generate a variety of color temperatures.

I hope this helps.

 

[sjastro]

Here is the solar spectrum.

The background or coloured region is the continuous blackbody spectrum.
The is due to the random walk mechanism for photons.
High energy photons emitted from fusion of nuclei in the core are almost instantly absorbed by matter and emitted in a random direction at longer wavelengths only to reabsorbed and reemitted in a different direction.
This process is repeated many times and the mean path length between collisions is around 0.1mm and lasts for over 500,000 years before the photon reaches the surface.

​

The black lines in the spectra are Fraunhofer lines where photons are absorbed by various elements in the Sun's photosphere.