Question of the Decade

[Deniz]

Can a beam of light be bent?

If so, what kind of force would it take?

I'd love to hear your opinions on this, and dont worry, I'm not building some sort of a doomsday device.

[Joseph_R_Thomas]

are u using a medium to bend it?
prism?

[galathaea]

Any differences in light propagation speed between two materials in contact can bend a light's path at the interface. Air and glass are two common examples, where we make things like glasses, microscopes, etc. Reflection (also due to media differences) is another example of bending light, as is the curvature of space time (though you then to detail more rigorously what is meant by bending as a geodesic might be thought of informally as "as straight as possible").

The momentum transferred by the bending of the light is easily calculated. You can define an effective momentum for light by the relation

E = p^2 / (2 m) (the kinetic energy equation, better known as 1/2 m v^2)

which rearranges to

|p| = √(2 m E)

More explicit values can be found by giving the energy equation of light, E = h n, giving

|p| = √(2 m h n)

That is the magnitude of the momentum, and the direction is the direction it is propagating. So changing the direction of the light will require the transfer of momentum in an amount equal to the difference between the two vectors.

This gives an easy calculation for quantities like an action impulse needed, but the question of force is ill founded. Any arbitrarily small force can cause any arbitrarily large momentum transfer, by merely acting for a long enough time. And without specifying the amount of "bending", any amount of force whatsoever will bend the light some if the force interacts electromagnetically.

[Deniz]

I'm curious, where did you copy/paste that from Galathea? Or did you actually go to all the trouble of typing it out from a book.

I'm not having a go at ya, I'd like to have access to the same sources of info, thats all. :)

[galathaea]

Actually, I didn't copy / paste, nor did I refer to any book in the process. I have this (annoying to some) "voice" I use in my posts (and in my notebooks), which can either sound educated or stuck up. Either way, it usually sounds like a text book, and I think the reason is because this is one of the two types of things I read most often. So its a comfortable "voice" for me.

But I didn't need to refer anywhere, because my degree was actually in physics, and this is all pretty low-level stuff. I think it just sounds different when I talk about materials of different speeds of light in contact instead of saying "use a lens", because I tend to focus on the abstraction that leads to the physics and mention the examples instead of focusing on the examples.

I don't know. Go figure.

[Deniz]

No worries then, I appreciate the honesty.

[Mick]

Originally posted by galathaea
Actually, I didn't copy / paste, nor did I refer to any book in the process. I have this (annoying to some) "voice" I use in my posts (and in my notebooks), which can either sound educated or stuck up. Either way, it usually sounds like a text book, and I think the reason is because this is one of the two types of things I read most often. So its a comfortable "voice" for me.

But I didn't need to refer anywhere, because my degree was actually in physics, and this is all pretty low-level stuff. I think it just sounds different when I talk about materials of different speeds of light in contact instead of saying "use a lens", because I tend to focus on the abstraction that leads to the physics and mention the examples instead of focusing on the examples.

I don't know. Go figure.

Made me get wood....

[Deniz]

Originally posted by Mick
Made me get wood....

anything makes you get wood

[Mick]

Originally posted by Deniz
anything makes you get wood

I am glad to see that people are following my woodage theory...

[souldog]

Ever since my days at the particle accelerator, I have a hard time
reading physics anymore (or getting wood for that matter. Too
many beam dumps I guess):D

[SolarFlare]

Originally posted by Deniz
Can a beam of light be bent?

If so, what kind of force would it take?

I'd love to hear your opinions on this, and dont worry, I'm not building some sort of a doomsday device.
Gravity well bends light... uh-oh, that's the second time I've said gravity well in CodeGuru today. Something's wrong.