The difference between light and illuminance or brightness

OI

Ok, this is a loser question but I am very new to physics.

I've recently been reading about light and how it may have the properties of both waves and particles. But how does illuminance travel, is that more like a wave. does illuminance travel through a vacuum. I can't seem to get my head around it.

I've only recently come across the lumen as a unit of measurement. Does brightness need molecules to travel. Sorry if this is kindergarten stuff.

OI

I think what I am trying to ask is this:

if you take the example of car lights, you can see them coming towards you from any distance providing the road is straight and flat, I assume that is light.

But those car lights only illuminate a relatively small section of the road in front of them, what is this beam, is it radiation of some sort?

Gurgle

OI wrote: »

I've recently been reading about light and how it may have the properties of both waves and particles. But how does illuminance travel, is that more like a wave. does illuminance travel through a vacuum. I can't seem to get my head around it.

In simple terms:

Light is the stuff that travels, ie wave/particles. Photons.

Illuminance is a measure of the rate of light arriving - light (photons) per square meter.

Brightness is measured at the source - the rate of emission of photons

Capt'n Midnight

It was thought that light waves needed a medium to carry it

but this expiriment back in 1887 did not detect the medium http://en.wikipedia.org/wiki/Michelson%E2%80%93Morley_experiment

Magnetic fields and electric fields have a short range.

A transformer converts electrical energy to magnetic energy and visa-versa. Something similar happens with the electrical and magnetic energy in light and radio and such like. Electromagnetic waves are self sustaining.


Another way is to treat light as a particle or as a wave as appropiate ( you can do the same trick with electrons ) if makes it easier.

Particles can travel through a vacuum easily enough.

OI

Thanks a lot lads, that makes things a lot clearer, was gonna use a silly science pun but reckon I don't have enough experience for that kind of behaviour.

Picked up a book today called spacecam for 8€, it's a load of pictures from space and includes pics from the Apollo missions to the Hubble telescope, can't believe the value. I know that's off topic but it's my thread and I can do whatever I want with it, stunning pics of nebula and galaxies and our solar system and disasters such as the 2004 tsunami from space