Light as a wave

[JustStuit]

Another question about simple physics I guess (im in 3rd year at high school so im here to learn)

why does light travel in a wave. wouldnt it travel the shortest distance, which would be a straight line. maybe im severely misinterpriting this, but u guyz could set me straight plz.

 

ps

the only reason i culd think of this is because of particles in the way, but what about in a vacuum?

 

Help plz

[JustStuit]

I was searching around the internet for a while to try to solve this and I found that light does travel in a straight line, but the curvature of spacetime explained in gr makes it a wave.

is this correct?

[CPL.Luke]

heres the basics of it.

 

are you familiar at all with basic electrostatics?

 

take the equation for the electric field of a point charge

 

E= k q/r^2

 

where E is the field strength and r is the distance from the charge. Now if you moved the charge back and fourth you would get a changing electrical field, one that (assuming the charge oscillated regularly) would give you a sine wave when you plotted the field strength against time. This is what light is. (classicly)

 

quantum mechanical description:

 

basics of it are that you have your wave, and that the wave is localised inside of a particle (whats known as a gaussian packet). Now the reason light acts like a wave when observed here is that the gaussian packet spreads over time, so in the brief period of time between emission and observation the packet grows and acts like a wave, then when its observed it gets localised again.

 

the bit about quantum mechanics is a bit hard for me to explain though so don't use it as cannon.

 

Edit: sorry you posted before I did so I didn't see your second post. A photon doe travel in a straight line but the curvature of space acts on it it follows the bend. this doesn't have much to do with light as waves though

[JustStuit]

ok thanks for the explanation

[Bubba]

JustStuit, first off good question.

 

light dose not travel in a wave because of particles in the way, in fact (loosely put)the wave oscillates in a perpendicular direction to the direction of travel.

think of a wave in the ocean. the wave front moves along at a steady speed, but the water is "pushed" up and down as the wave passes. Hence the wave travels in a straight line horizontally forward, while the water is oscillated up and down.

 

Photons (Light) consist of an electric and magnetic field which oscillate horizontally and vertically with respect to the forward direction of travel. if you were to "look" at a photon coming towards you the electric and magnetic fields would trace out a cross, +, as the photon approached.

 

ps. unlike with the water wave, a photon dose not actually cause an oscillation unless it is absorbed.

[5614]

if you were to "look" at a photon coming towards you the electric and magnetic fields would trace out a cross, +, as the photon approached.

Just to expand/explain that it is because you see the magnetic field of light going left right, so you'd see - for the magnetic field... and then the electric field goes up and down, so you'd see | for the electric field, because light is both of these put together you get a + shape.