Optics: light beams

[Jake712]

Why, whenever you are outside at night, do all of the lights extend into beams of light perpendicular to your vision?

 

For example, when driving, the cars coming towards you on the other side of the road have lights that create a beam upwards and towards the ground...

 

Or, when looking at a street light which has lights extending in five directions...

 

Thanks

[granDODyssey]

light can be created by heat, by chemical reaction, by electrical source or by nuclear reaction...etc..

but whatever the source, it always involves electrons moving up and down their orbits around the nucleus of the atoms of the light source.

when the electrons gains energy by some means, the go up to the higher orbits but they can't stay forever in the higher energy state...and eventually they will go down to the normal orbit releasing (energy)what they have taken as photons ( light).

 

As you can imagine, electrons are orbiting the nucleus at high speed, it is not possible for them to emits the photons into specific direction under normal circumstance.

So you can assume that the photons are emitted into all direction at it's source level.

 

so..you can see light from any angle...

 

the car head light is a focused light beam redirecting most ray of light into one direction by mean of reflection..

the laser is another focused light beam redirection almost all ray of light into one

direction... ;-)

[swansont]

light can be created by heat' date=' by chemical reaction, by electrical source or by nuclear reaction...etc..

but whatever the source, it always involves electrons moving up and down their orbits around the nucleus of the atoms of the light source.

[/quote']

 

No it doesn't.

 

EM radiation is also emitted when free electrons are accelerated. The source of the acceleration can be scattering from thermal motion, as in a filament of an incandescent light.

[granDODyssey]

i guess you are right... i heard that EM radiation is also emitted in things like particle accelerators...( i think i should have said that the electron release photon when they move to lower energy state...without the words "orbits" , "nucleus" etc...)

 

but one question ...when you accelerate a charged particle like electron....say.. you give the kinetic energy to the electron ....and so the electron becomes energetic ( say higher energy state ) ....and i believe that the electron will release the energy when a collision occurs or when it becomes decelerated(say lower energy state)....right? ..correct me if i am wrong ...thanks.

[Guest DarkEcho]

I'm not sure thats what he was asking about

What i think he was asking is why when you look at bright lights you get radial lines appearing from the point. If so you might try asking in the physiology forum.

[swansont]

i guess you are right... i heard that EM radiation is also emitted in things like particle accelerators...( i think i should have said that the electron release photon when they move to lower energy state...without the words "orbits" ' date=' "nucleus" etc...)

 

but one question ...when you accelerate a charged particle like electron....say.. you give the kinetic energy to the electron ....and so the electron becomes energetic ( say higher energy state ) ....and i believe that the electron will release the energy when a collision occurs or when it becomes decelerated(say lower energy state)....right? ..correct me if i am wrong ...thanks. [/quote']

 

When you use "energy state" it implies quantized states, which are bound to an atom or molecule. Free electrons are in the continuum.

[Jake712]

yes DarkEcho, thats what i was talking about

I will post again in the physiology forum.

 

Sorry for the mistake.

[swansont]

Why' date=' whenever you are outside at night, do all of the lights extend into beams of light perpendicular to your vision?

 

For example, when driving, the cars coming towards you on the other side of the road have lights that create a beam upwards and towards the ground...

 

Or, when looking at a street light which has lights extending in five directions...

[/quote']

 

I've been poking around, looking for this, because I thought it had a special name, but I can't find it. I think you are talking about an effect similar to a star filter or lens flare only with the eye. I get this when I squint. It's a diffraction effect from the constricted pupil. You can also see it if you look through an irregularly-shaped pinhole - you get diffraction from the edges, and it's more noticable when the edge effects can't be ignored.