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Bending of light rays?





yagnyavalkya
If light rays bend near high mass bodies
then why does the light ray emanating from the high mass body show this curvature of spacetime
let me explain
for example "During solar eclipses, for the first time, phenomena of gravitational bending of course of light beams near dense mass could be recorded, which became one of the first experimental proofs for conclusions about general relativity theory"
Now let us consider this the light ray passing near the sun gets bent they why does not a light ray actually emitted by the sun very much near the same spacetime as the bent light ray from the distant star not bend
Bikerman
The gravitational effect on an emitted photon is well understood. The observed effect depends on the gravitational potential (ie the difference in gravitation between the emitter and the observer). Where the difference is positive there will be red-shift. Where the difference is negative there will be blue-shift.
There will be very slight bending of the photons path, depending on the angle of emission.
yagnyavalkya
Bikerman wrote:
The gravitational effect on an emitted photon is well understood. The observed effect depends on the gravitational potential (ie the difference in gravitation between the emitter and the observer). Where the difference is positive there will be red-shift. Where the difference is negative there will be blue-shift.
There will be very slight bending of the photons path, depending on the angle of emission.

"The gravitational effect on an emitted photon is well understood."
I dont understand the photon is bending because of the spacetime curve near a high mass body
what is the gravitational effect of an emitted photon
wont the same spacetime curve bend the photon emited by the high mass body itself
is it true that there is no gravitational force as such but it is bending behavior is attributed to this
Bikerman
As a photon clims out of the Sun's gravity well the frequency is shifted towards the less energetic end of the spectrum - redshift. As the photon enters the Earth's gravity well it is shifted towards the more energetic end of the spectrum - blueshift. The difference (the gravity potential) determines the final amount of shift observed.

Yes, the photon will 'bend' to follow the curvature of spacetime - as predicted by GR - but that curvature is very tiny for a photon emitted from the sun (depending on the angle of emission and the position on the sun's surface).
DoctorBeaver

diagram courtesy of NASA

That gravity bends light can be seen in the effect known as "gravitational lensing". This is where the light is bent to the extent that an object appears to be in a different place, as shown by the diagram.

In the particular instance in the diagram, there appear to be 2 quasars at different points in the sky when, in fact, there is only 1.
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