Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: thedoc on 08/03/2016 22:50:01

Title: Is the range of electromagentic radiation limited?
Post by: thedoc on 08/03/2016 22:50:01
John Lindop asked the Naked Scientists:
   Why  is  there  just  a  specific ,  limited,  rang  of  frequencies of  electro  magnetic  radiation ?
What do you think?
Title: Re: Is the range of electromagentic radiation limited?
Post by: PmbNEP on 09/03/2016 04:37:41
Realistically, there is no upper or lower limit to the energy that a photon can have.
Title: Re: Is the range of electromagentic radiation limited?
Post by: Ethos_ on 09/03/2016 05:02:00
Quote from: PmbNEP on 09/03/2016 04:37:41
Realistically, there is no upper or lower limit to the energy that a photon can have.
Is that you Pete? Surely it must be so welcome back, it's very good to see you posting here again.................Ethos
Title: Re: Is the range of electromagentic radiation limited?
Post by: Space Flow on 09/03/2016 08:35:25
Quote from: thedoc on 08/03/2016 22:50:01
John Lindop asked the Naked Scientists:
   Why  is  there  just  a  specific ,  limited,  rang  of  frequencies of  electro  magnetic  radiation ?
There is a limit at one end because of the planck scale. That sets a limit on how small a wavelength and as such how high a frequency EMR can have. 
At the other end of the scale it would depend on whether you subscribe to infinity or not. The wavelength can of course not be more than 2r, where r is the radius of the Universe.You can not have a wavelength that is longer than the Universe.   
On a more realistic level, it is not possible for us to even hypothetically detect a wavelength the size of our observable universe. Yet that is the last thing we will see when expansion equals the speed of light. (if we could see it that is.)
Title: Re: Is the range of electromagentic radiation limited?
Post by: evan_au on 09/03/2016 09:07:19
We give names to specific subsets of the electromagnetic spectrum, but there are photons at both ends beyond the named ranges (even though we don't see them very often on Earth).

See the table at: http://en.wikipedia.org/wiki/Electromagnetic_spectrum
Title: Re: Is the range of electromagentic radiation limited?
Post by: jeffreyH on 19/03/2016 14:18:40
If the universe as we know it is all there is then the longest wavelength may well be finite. If there is an infinite cosmic bulk then an infinitely long wavelength would have zero energy. Given this the only wavelengths of interest must have finite dimensions.
Title: Re: Is the range of electromagentic radiation limited?
Post by: JoeBrown on 19/03/2016 23:01:37
What's the lowest frequency to propagate in a vacuum?

Based on the wiki, limited by the atmosphere, does that hold true for outer space?
Title: Re: Is the range of electromagentic radiation limited?
Post by: alancalverd on 19/03/2016 23:13:14
There is no theoretical lower limit.

Since E = mc2 = hν, the upper limit of ν is where the entire mass of the observable universe is converted into the energy of a single photon.
Title: Re: Is the range of electromagentic radiation limited?
Post by: JoeBrown on 19/03/2016 23:45:33
Since there's a space station floating around, experimenting on stuff, thought maybe they had shed some light on the topic.  But suspect physical constraints, might be plentiful there too.

I curious if a photon has any physical constraints that have been identified.
Title: Re: Is the range of electromagentic radiation limited?
Post by: jeffreyH on 19/03/2016 23:50:18
Quote from: alancalverd on 19/03/2016 23:13:14
There is no theoretical lower limit.

Since E = mc2 = hν, the upper limit of ν is where the entire mass of the observable universe is converted into the energy of a single photon.

What happens as the wavelength approaches the Planck scale?