Thread: Deflection of light in classical physics

1. We want to find deflection of light in classical physics considering light as any other object (Tangent lines to circles - Wikipedia, the free encyclopedia I couln't find a better picture)

suppose light is travelling from q to P (7.5*10^10 cm, which we consider the x-axis with origin at O), space is measured in light-second, so x= 1 (= 3*10^10 cm)
distance OP (R) is 2.5 c
F_P = GM/ R^2 k = 23 593 at P (x=0)
Please tell me now if the following is right, or correct what is wrong:

- the total force F acting on light from -200 (sec) to P is the integral of cos * GM /D^2 = 2.5 * k = 59000
(but it has the units of velocity)

- the total deflection of light = F_T =( t: -200 - 200 sec) 59000*2 = 118000 / C

is this correct so far?  2.

3. Originally Posted by whizkid I hope Harold can say a resolutive word also about this problem: we want to find deflection of light in classical physics considering light as any other object (Tangent lines to circles - Wikipedia, the free encyclopedia I couln't find a better picture)

is this correct so far?
No, this is not how is done. But it will not stop you from posting errors.  4. If you consider light as you would any other object, then it would follow a hyperbolic trajectory.

The angle of deflection for a hyperbolic orbit is found by the relationship b is the "impact parameter" or the closest approach the two objects would have made without gravity.
v is the starting velocity of the deflected object, which in this case equals c.

If you use the Sun for M and its radius for b, you get an answer of ~.875 degrees, which is in the order of 1/2 the value you get with GR. (Which is what you should expect, because the Newtonian answer works out to be 1/2 of the GR answer.  5. Originally Posted by Janus  If you use the Sun for M and its radius for b, you get an answer of ~.875 degrees,
thanks, Janus
.875 degrees or seconds?
can you give me a link where to find info about recent experiments of deflection  6. deflection of light in classical physics
I think you mean "non-relativistic physics", not "classical physics". Classical physics encompass anything where quantum effects do not play a role, including GR; non-relativistic physics encompass scenarios where relativistic effects can be neglected ( can be both classical or quantum ).  7. Originally Posted by Markus Hanke Classical physics encompass anything where quantum effects do not play a role, including GR; non-relativistic physics encompass scenarios where relativistic effects can be neglected ( can be both classical or quantum ).
Thanks, Markus, I ignored the difference,
you mention quasar experiments, can you give me a link where to find details?

Thanks a lot  8. Originally Posted by whizkid
please explain why we cannot use the Newronian formula F = V^2/R for the deflection of light?
First off, the correct formula is F=m*V^2/R, not F = V^2/R. You need to learn to get your basic formulas right.

Second off, F=m*V^2/R applies to particles that have mass, the photon DOESN'T, so the formula DOES NOT apply. This is why Soldner et al. got the wrong result.

In order to get the right result, you need to learn GR. In order to learn GR , you need to learn calculus, something that you prefer to avoid in favor of trolling this forum.  9. Originally Posted by Janus If you consider light as you would any other object, then it would follow a hyperbolic trajectory.
Thanks Janus,
Is trajectory different if you consider it like any other object?

thanks  10. Originally Posted by Janus v is the starting velocity of the deflected object, which in this case equals c.
.
Can you explain why deflection is v/c (or give me any link) ? is v = 118 000 (is itcm/s?), the integral of the force acting on the photon?

can we apply this procedure to the earth orbiting the sun?
The earth gets roughly 1 cm/s^2 , in 400 sec it gets 400 (?) the initial velocity is 10^6, deflection is 400/10^6 = 0.0004? is this value in degrees or seconds?  