Do radio waves degrade over distance?

[jgrabham]

OK, was on bitesize (exams next week :[) and it said Do radio waves

Increase in intensity over distance
Decrease in intensity over distance
Stay the same intensity over distance

It says its the first one - I disagree, I would say it only decreases in intensity if its going through matter. What do you think?

[madmetal]

OK, was on bitesize (exams next week :[) and it said Do radio waves

Increase in intensity over distance
Decrease in intensity over distance
Stay the same intensity over distance

It says its the first one - I disagree, I would say it only decreases in intensity if its going through matter. What do you think?

http://en.wikipedia.org/wiki/Radio_propagation
and happy studying for exams :)
what do you study?

[jgrabham]

http://en.wikipedia.org/wiki/Radio_propagation
and happy studying for exams :)
what do you study?

Its just GCSE science

[shavenlunatic]

as he's in greece, I doubt he knows what a GCSE is... :)

[mips]

OK, was on bitesize (exams next week :[) and it said Do radio waves

Increase in intensity over distance
Decrease in intensity over distance
Stay the same intensity over distance

It says its the first one - I disagree, I would say it only decreases in intensity if its going through matter. What do you think?

You are wrong on the first choice. If it was the case you and i would both be multi millionares by now.

Radio wave propagation is very much dependant on the frequency of the radio waves.

Radio waves are nothing but energy.

You should have picked option number two.

[koenn]

Radio waves are nothing but energy.
You should have picked option number two.
If radio waves are nothing but energy,
and their intensity decreases over distance,
where does the (lost) energy go ?

[MacScotland]

It just "thins" out proportional to the square of the distance, like a ripple on a pond.

[jgrabham]

It just "thins" out proportional to the square of the distance, like a ripple on a pond.

Energy doesnt just disapear; it has to go somewhere

[jgrabham]

as he's in greece, I doubt he knows what a GCSE is... :)

BTW, I'm in year 10, I get 2 GCSEs in science I do one in year 10, then the 2nd in year 11. (providing I pass my exams)

[JC_510]

I got an 'A' in GCSE double science last year, but this question is a bit tricky.

You must have been taught that the speed of light cannot be exceeded by anything. So if these radio waves are already travelling at light speed, how can their speed increase with distance travelled?

I would say it would depend what they were travelling through, but in most cases, I would assume that they would travel at constant velocity. :confused:

Im going to put some work in and research this, if I decide on an answer to the question, I'll post it here!!

[milton1]

Energy doesnt just disapear; it has to go somewhere

The energy is not disappearing. It is simply dispersing. If the original source of the signal sends out a spherical wavefront, then the surface area of the front will increase as r^2. This means the energy density on that front will decrease as r^2. Thus, unless the signal is 100% coherent (not actually possible), it will decrease in intensity as it propagates through space (or any other media).

[jgrabham]

You must have been taught that the speed of light cannot be exceeded by anything.here!!

I'm always arguing with my Physics teacher about this - There probabally is a way, and this is traveling through space - what about not traveling through space (wormhole type things)

[douseej85]

They stay the same over distance, although if you get feedback from the wave (a return signal after bouncing off something) it can appear weaker because the wave spreads out over distance..

The energy isn't being lost, (as asked previously) it's just spreading so thin over time/distance that it's becomming less and less until you can't detect it..


Example, do detect planet people are firing beams or radio waves into space, with huge amounts of power and getting the faintest signal in return...I would draw a diagram if poss but ahh well...



)))))))


Not the best as the lines get thicker, but as mentioned before with "ripples in a pond", just because you can't 'see' the water still rippling, doesn't mean it isn't, then energy diplaced is just becomming thinned out until you can't detect it by eyesite,

Tests done actually showed in an olympic swimming pool ripples carried on for 28mins after people couldn't 'see' them any more, and with higher sensitivity equipment they would have prob carried on longer.

At which point the energy would either be absorbed or converted

[Ireclan]

I myself always thought radio waves stayed the same over distance...Guess I was wrong, because that really doesn't make sense, now that I think of it.

EDIT-Wait, so I'm right, in a way? Cool!

[milton1]

Intensity=Power/Area
Power is fixed by the source. Area goes up, intensity goes down. Plain and simple.

[DarkN00b]

I'm always arguing with my Physics teacher about this - There probabally is a way, and this is traveling through space - what about not traveling through space (wormhole type things)

Energy travelling through a wormhole would in all probability still not exceed the speed of light. It would only seem to do so because it would be taking a shortcut outside what we think of as normal space/time from point A to point B. The speed would depend upon the (density? amount of curvature?) of the space within the wormhole.

[MarkX]

Duh.
Do ripples in a pond get bigger as they move outwards?
Use your noddy.

[orange2k]

Can you listen to Zagrebs Radio101 on 101mHz right now over your radio?....
I guess you can`t...
So...

[jgrabham]

Can you listen to Zagrebs Radio101 on 101mHz right now over your radio?....
I guess you can`t...
So...

Thats irrelivant, as there is stuff (very technical) in the way - I'm talking about through a vacume / space

[orange2k]

I don`t think they degrade fast in space...
You probably got to have an amplifier, though, to pick up the signal...
Thats probably why they are listening to extraterrestial signals over a BIG antenna at the SETI...

[jgrabham]

I don`t think they degrade fast in space...
You probably got to have an amplifier, though, to pick up the signal...
Thats probably why they are listening to extraterrestial signals over a BIG antenna at the SETI...

Yes, but theyre not listning to us, as we are fairly sure there is no intelligant life within 150 lightyears. (could be wrong though)

[MacScotland]

Have a look here http://www.antonine-education.co.uk/physics_a2/Module_4/Topic_4/topic_4.htm

[jgrabham]

Have a look here http://www.antonine-education.co.uk/physics_a2/Module_4/Topic_4/topic_4.htm

Wow, thats complicated - 3 years till I have to do that! (well, no because I probabally wont do physics at AS or A2)

[MacScotland]

Or here http://en.wikipedia.org/wiki/Inverse-square_law

[MacScotland]

This might help too http://www.bbc.co.uk/schools/gcsebitesize/physics/

[jgrabham]

Or here http://en.wikipedia.org/wiki/Inverse-square_law

Wow, too tired to be bothered to read that, thanks anyway.

[orange2k]

I think thats all about the BIG antenna stuff, the more further away you go...:)

[MacScotland]

Yeah the first link was probably a bit too complicated for you now - but do check out wiki & BBC.

[madmetal]

as he's in greece, I doubt he knows what a GCSE is... :)

yeap but google is a good friend ;)
http://en.wikipedia.org/wiki/GCSE


and surprising i am a poolie and sad about dimi left the club... :KS

[jgrabham]

Not very accurate -
final examinations are then taken at age 16 (Year 11/Year 12).

I'll be 15 when I do mine (doing a load of modulars and coursework now anyway)

[jgrabham]

BTW - this is the course I have to do - http://www.gcse-science.com/media_subpage.php?pg_id=127

Hooray, I'm a guinea pig!

(If this pilot scheme fails does it mean my 2 years of work and exams mean **** all?)

Better site - http://www.21stcenturyscience.org/

[satx]

Radio waves decrease in intensity/energy because of the impedance of free space. That impedance is 377 Ω. Free-space power loss is proportional to the square of the distance between the transmitter and receiver, and also proportional to the square of the frequency of the radio signal.

FSL= (4xPIxFrequency/c)^(2), where c is the speed of light.

Bottom line- energy is dissipated as the square of the distance between transmitter and receiver.

[mips]

I'm always arguing with my Physics teacher about this - There probabally is a way, and this is traveling through space - what about not traveling through space (wormhole type things)

Wormholes do not increase your velocity, they merely shrink space. So you are still traveling at c but the distance is shorter.

[jgrabham]

Wormholes do not increase your velocity, they merely shrink space. So you are still traveling at c but the distance is shorter.

They shrink space? I thought they were just a rip where you could jump through to a parallel bit of space? (space isn't like a big ball, its like spaghetti - it goes all over the place

[mips]

They shrink space? I thought they were just a rip where you could jump through to a parallel bit of space? (space isn't like a big ball, its like spaghetti - it goes all over the place

http://en.wikipedia.org/wiki/Faster-than-light#Option_F:_Distort_the_space-time_fabric
http://en.wikipedia.org/wiki/Wormhole
http://www.usd.edu/phys/courses/phys300/gallery2/dave/dave.htm

Enjoy!