Bending of light in a uniform gravitational field

[vuser88]

Homework Statement

This is supposed to be a simple problem that shows that light bends or gets pulled in a gravitational field.


A light pulse emitted in the positive x direction travels 10 s in a uniform gravitational field of 100 m/s^2. the gravitational field points in the negative y direction. find the displacement of the light pulse in the y direction.

help, i don't even know the equations relating the two. any help would be greatly appriciated.

i don't even know how to relate the two. we were given only one equation.

Homework Equations

u_y = c (1 – v2/c2)1/2

The Attempt at a Solution

dont even know where to start. i understand that light will be curved down. it travels at the speed c for 10 seconds so that gives me a distance... but that as far as i can get

this is an intro class to cosmology

thank you for any help.

 

[vuser88]

Btw can anyone suggest some good intro books to comsology that has lots of examples. the one we are using is by ryder. there are no examples

 

[cragar]

you can use E=mc^2 hf=mc^2 , to get an effective mass for the photon and then use Newtons law for gravitation to get an estimate of the force between them. But i think its off by a factor of 2 from GR.

 

[vuser88]

But how would the force help me... I am thinking that this can be treated like a free throw problem... but I am not sure...thnk u

 

[rude man]

Cragar is right. Using Newton would understate the effect by about 2:1.

This requires the General Theory of Relativity.

 

[vela]

You could resort to using an argument based on the equivalence principle, but I think you'd be begging the question. You're probably expected to do the calculation using GR.

Do you have the spacetime metric that corresponds to a uniform gravitational field?

 

[vuser88]

We didnt talk about metrics bc the class is supposed to not cover and mathematics of GR. Should i assume a metric.
How would i go about solving it then if i shouldn't use Newtons method...

 

[rude man]

Might look at this.

http://www.einstein-online.info/spotlights/equivalence_deflection