Talk:Light

Article Checklist for "Light"

Workgroup category or categories	Physics Workgroup [Categories OK]
Article status	Developing article: beyond a stub, but incomplete
Underlinked article?	No
Basic cleanup done?	Yes
Checklist last edited by	Robert W King 14:04, 6 June 2007 (CDT) Matt Mahlmann 17:52, 7 June 2007 (CDT)

To learn how to fill out this checklist, please see CZ:The Article Checklist.

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Moving Quantum section

...into the greater narrative to make the entry less WP-like.--Robert W King 10:32, 7 June 2007 (CDT)

Reinstated QM - as light IS QM in effect and description. - you may consider this an editor decision. Robert Tito |  Talk 

Photoelectric effect

The basic idea is that individual photons carry a fixed amount of energy. It increases with frequency (which is why X-rays and UV light can be dangerous), but is otherwise fixed. Now, if you shine a bright light on an electric plate many, many photons will collide with the plate, potentially displacing electrons when they do. There is a certain amount of energy needed to displace an electron from an atom, creating current (or a "click" from a detector). As you start to reduce the light level, the number of photons is reduced, but not the energy. This means that individual photons are still able to displace electrons, but there are fewer of them, and so fewer clicks.

Incidentally, Albert Einstein received the Nobel Prize for his work on the photoelectric effect. Greg Woodhouse 14:49, 7 June 2007 (CDT)

Article needs work

More generally, there are a number of inaccurate or misleading statements in this article. I'm afraid I'm in a bit of a rush and can't really point them out just now, but I'd start with the introduction: light is not the same thing as the transition between energy levels that can cause atoms to emit photons. Greg Woodhouse 15:07, 7 June 2007 (CDT)

I fixed the wording; I hope the intro is more accurate now. The article was only created yesterday.--Robert W King 15:19, 7 June 2007 (CDT)

I understand that, and I didn't mean to be rude. As it happens I had to run (two, no three meetings) and I was trying to say what I wanted to say too quickly. Greg Woodhouse 17:46, 7 June 2007 (CDT)

Defining light

The definition really needs to be changed because it describes one (and by no means the only) mechanism for generating light. Light is electromagnetic radiation falling in a rather narrow frequency band. I'm going by memory here (so look it up), but I believe it's between about 3 x 10^14 and 6 x 10^14 Hz. NASA has a number of educational articles that provide more background.

The important thing here is energy. Anytime you generate photons that fall in the range of about 1.2 to about 8 electron volts (eV) you are generating visible light, regardless of the mechanism. Again, you should look those numbers up (I don't have a table in front of me). Greg Woodhouse 13:24, 8 June 2007 (CDT)

hold it: light also IS invisible light, from hard röntgen to IR wavelengths. Robert Tito |  Talk  13:30, 8 June 2007 (CDT)

I'm getting there, eventually. I realize the article is far from complete. --Robert W King 13:53, 8 June 2007 (CDT)

Well, people do sometime refer to "ultraviolet light" and maybe even infrared (but I hear that less often). I've tended to prefer a narrower range and to speak of ultraviolet radiation (and similarly for infrared), but I'm not an expert. I wonder if there isn't some variation across disciplines here? Greg Woodhouse 14:13, 8 June 2007 (CDT)