Predicting angle of deflection of light

In summary, in the conversation, the speaker asks for an explanation of the equation for calculating the angle of deflection for light approaching a massive body and what "1.7 seconds of arc" means. The other person explains that the equation was made to match observations and that small angles are described in minutes and seconds of arc. They also clarify that the equation is used to quote the result and provide an alternate way of expressing it. Finally, the speaker asks about a specific part of the equation and the other person explains how it relates to the distance from the center of the Sun.
  • #1
William Henley
Hello,
I was recently reading relativity the general and special theory by Albert Einstein. When I came across the equation to calculate the angle of deflection for light as it approaches a massive body. I was just wondering if someone could explain why this works and also what "1.7 seconds of arc" means, as it is part of the equation.
 
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  • #2
William Henley said:
I was just wondering if someone could explain why this works
The theory was made to match observations. What exactly do you mean with "this"?

Small angles are described with minutes and seconds of arc. 1 degree = 60 minutes = 3600 seconds.
 
  • #3
mfb said:
The theory was made to match observations. What exactly do you mean with "this"?

Small angles are described with minutes and seconds of arc. 1 degree = 60 minutes = 3600 seconds.
Oh what I mean is what do the parts of the equation mean.
 
  • #4
mfb said:
Small angles are described with minutes and seconds of arc. 1 degree = 60 minutes = 3600 seconds.
Oh yeah thanks, so is this what used to predict the angle of deflection?
 
  • #5
William Henley said:
Oh what I mean is what do the parts of the equation mean.
That depends on the equations, there are different ways to derive that result and I don't know which set of equations you are looking at. I also don't know how much you know about general relativity.
William Henley said:
Oh yeah thanks, so is this what used to predict the angle of deflection?
This is used to quote the result. It is just a unit, like meters for length, seconds for time or degrees for angles.
Instead of 1.7 seconds of arc, you can also say "an angle of 1.7/3600 degrees".
 
  • #6
mfb said:
That depends on the equations, there are different ways to derive that result and I don't know which set of equations you are looking at. I also don't know how much you know about general relativity.
This is used to quote the result. It is just a unit, like meters for length, seconds for time or degrees for angles.
Instead of 1.7 seconds of arc, you can also say "an angle of 1.7/3600 degrees".
I'm talking about a=1.7 seconds of arc over delta
 
  • #7
William Henley said:
I'm talking about a=1.7 seconds of arc over delta

The formula you are talking about comes from the formula

[tex] \theta = \frac{4GM}{rc^2}[/tex]

Where r is the distance from The center of M that the light passes. The answer will be in radians

Basically if you use the mass of the Sun for M, set delta equal to 1 solar radius for r, and convert it to give an answer in second of arc rather than radians, you get

[tex]\theta = \frac{1.7}{\Delta}[/tex] seconds of arc.

For the angle of deflection of light passing at a distance of delta from the center of the Sun where delta is measured in sun radii.
 
  • #8
Janus said:
The formula you are talking about comes from the formula

[tex] \theta = \frac{4GM}{rc^2}[/tex]

Where r is the distance from The center of M that the light passes. The answer will be in radians

Basically if you use the mass of the Sun for M, set delta equal to 1 solar radius for r, and convert it to give an answer in second of arc rather than radians, you get

[tex]\theta = \frac{1.7}{\Delta}[/tex] seconds of arc.

For the angle of deflection of light passing at a distance of delta from the center of the Sun where delta is measured in sun radii.
Ok yeah that makes sense, thanks for the answer.
 

What is the angle of deflection of light?

The angle of deflection of light is the change in direction of a light ray when it passes through a medium with a different refractive index. It is caused by the change in speed of light as it travels from one medium to another.

How is the angle of deflection of light calculated?

The angle of deflection of light can be calculated using Snell's Law, which states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is equal to the ratio of the refractive indices of the two media.

What factors affect the angle of deflection of light?

The angle of deflection of light is affected by the refractive indices of the two media, the angle of incidence of the light ray, and the wavelength of the light. The refractive indices of the media determine how much the light will bend, while the angle of incidence and wavelength affect the overall direction of the light.

Why is predicting the angle of deflection of light important?

Predicting the angle of deflection of light is important in various fields such as optics, astronomy, and engineering. It helps in designing lenses and optical instruments, understanding how light behaves in different media, and predicting the appearance of objects in different conditions.

What are some practical applications of predicting the angle of deflection of light?

Predicting the angle of deflection of light is used in the manufacture of lenses for eyeglasses, cameras, and microscopes. It is also important in understanding how light travels through the atmosphere, allowing us to predict the appearance of objects in different weather conditions. In addition, it is used in the design and construction of optical devices such as telescopes and fiber optic cables.

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