Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: mike2niner4 on 19/06/2009 16:42:22

Title: Help With Rays/Waves
Post by: mike2niner4 on 19/06/2009 16:42:22

Hey,

I'm wondering if somebody can help explain to me about waves/rays in a physical way. For example, i know Alpha radiation is a helium nucleus, beta an electron and gamma a ray, but are rays physical matter?

I dont know if i make any sense but i want to get an image in my head of what they are in terms of the physical bits.

Thanks, Mike

Title: Help With Rays/Waves
Post by: lightarrow on 19/06/2009 19:52:24

Quote from: mike2niner4 on 19/06/2009 16:42:22

Hey,

I'm wondering if somebody can help explain to me about waves/rays in a physical way. For example, i know Alpha radiation is a helium nucleus, beta an electron and gamma a ray, but are rays physical matter?

Gamma rays don't have mass so you shouldn't call them "matter".

Quote

I dont know if i make any sense but i want to get an image in my head of what they are in terms of the physical bits.

All of those you mentioned can be visualized as tiny particles. In the case of the gamma, however, you can't have an idea of their "dimensions".

Title: Help With Rays/Waves
Post by: lyner on 20/06/2009 00:29:29

The term 'rays' is an old fashioned one and was coined before people had sussed out what was happening in nuclear and other reactions.  The term includes particles and waves - so it isn't much used these days (except when talking about alpha beta and gamma 'rays').
Waves are better defined, though.

Title: Help With Rays/Waves
Post by: JP on 20/06/2009 04:59:33

Additionally, you may hear the term "ray" describing light, as in "light rays," which are approximations to the real underlying light waves.  It's usually much easier to figure out how light travels by just drawing rays than to calculate how the waves travel, and so they're used a lot as tools to design systems.  Rays aren't a real thing, however, as they're just approximations to the real underlying processes.

Title: Help With Rays/Waves
Post by: lyner on 21/06/2009 23:25:32

Quote

"light rays," which are approximations to the real underlying light waves

Perhaps it would be better to call light rays "an alternative way of thinking about what happens to light, when it travels from place to place".
Rays of light are a bit like Magnetic Lines of Force. They aren't 'really there' but they help in explanations and calculations. Waves can be very tiresome to analyse.

Title: Help With Rays/Waves
Post by: lightarrow on 22/06/2009 12:32:48

'Rays' of light are useful in the so called 'geometrical optics' approximation: wavelenght of light much smaller than all the other significant dimensions in the system considered. Otherwise the term is wrong (diffraction, interference, ecc) and we have to use the wave description.
In the case of gamma radiation, that approximation is satisfied, excepting very special cases and so you can call them 'rays'.