light advice!

[epilot]

Hello,

don't know if this is a suitable forum for my question or not but i'd like to know why the light of a spotlight propagates as a beam with an incrasing in diameter of light at distances.
As I know a light beam travels at direct lines, so why the light of a spotlight changes in diameter as it travels?!

Thanks

 

[Papabravo]

The reflector in the light is not a perfect curve and the rays of light are not all parallel. This defect causes the beam to diverge. This also happens with other types of waves including RF and sound.

 

[n.house]

You sort of answed your own question. Light travels in an aproximatly straght line in quatums but your standard light source transmits these quantums all over the place hence the scattering, lasers on the other hand......

 

[jbeng]

Laser beams will also diverge to some extent, also due the the imperfections in the resonator mirrors or other optical elements. The divergence is usually so small it's measured in milliradians.
JB

 

[Hero999]

Imagine a omnidirectional light source like the sun. All the light emmitted from it travels in a straight line, it's just that the lighe is being emmitted from all angles so there are so many lines.

 

[n.house]

Yes I know lasers will diverge but not as much as a standard light source, I just couldn't be arsed to expain it......

 

[Hero999]

Of course there's diffration and a large mass can deform space and time causing the light to bend slightly. When unhindered light will always travel in a straight line.

 

[n.house]

OK, here we go, light is emmited in quantums, any mass be it a molicule or a star will have an effect on the quantum. This means that in the real univeres it does not travel in a straight line (I know this is a bit perdantic, and I can't spell) in a perfect vacuum you are correct, but we havent got one!