# A contiguous spectrum?

1. Jun 2, 2005

### curvedlogic

I have always visualized light as a series of discrete packages of energy. It seems fairly straight forward...at least until goes into more detail, but the smooth transition into a radio wave leaves me confused.

Is there some specific point at which a radio wave becomes contiguous?

2. Jun 2, 2005

### ZapperZ

Staff Emeritus
Er... have you tried looking at the spectrum from an ordinary lightbulb using a spectrometer? A prism? It's not "discrete" at all!

The amount of energy being carried is continuous. But the variation in frequency/energy need not be. What this implies is that if you fix a frequency of light, the energy is being carried in discrete bundles of hf, where h is the Planck constant, and f is the frequency. However, "f" can vary continuously if we use something like a tungsten filament, or a synchrotron light source. Only in certain situations such as atomic transition or lasers do you get these to be vary discretely. This is all due to the "boundary conditions" of the source.

Zz.

3. Jun 2, 2005

### curvedlogic

Okay, I can visualize it until I extrapolate downwards, to say, Long Wave radio. There I imagine the broadcaster saying something like... "there will be a short intermission while we wait for the next package of our radio waves.

Joking aside, I will give some thought to your answer tonight. At the moment I can't see how this is reconcilable with how I imagine a discreet photon in the light frequency range. CL.

4. Jun 7, 2005

### McQueen

I have always visualized light as a series of discrete packages of energy. It seems fairly straight forward...at least until goes into more detail, but the smooth transition into a radio wave leaves me confused.

Is there some specific point at which a radio wave becomes contiguous

Two factors are involved . The first has to with wave particle duality and the formula e = hf , which states that the energy of EM radiation varies with its frequency , high frequency radiation such as light has more energy and thus exhibits particle like properties. Lower frequency radiation such as is found in radio waves has less energy and therefore exhibits wave like properties. The second factor involves the manner in which these two types of radiation originate. While high frequency radiation is thought to be emitted directly by electrons , lower frequency radiation is emitted due to the jiggling or oscillation of ions and the acceleration of electrons. The question of where one type of EM radiation begins and the other ends is interesting , although cascade lasers have been shown to emit photons with wave lengths of 0.001m , so the transition if it exists must take place at around this wave-length .

5. Jun 20, 2005

### curvedlogic

Eye surgery has seen me out of the loop for a while...:yuck: but a late thanks for that, McQueen

6. Jul 13, 2005

### DaveC426913

BTW, don't think of light and radio (or any other EM freq) as distinct types of radiation. Our designations of them as "this is a radio freq and that is a microwave freq" are entirely humano-centric. A given photon does not know or care if it is perceived as microwave or radio or visible light. Either it can penetrate a substance or it can't.