# Gravitational Lense - Focal Point & Mass-Radius Formula

• scupydog
In summary, the conversation discusses the existence of a focal point in a gravitational lens and whether there is a formula that relates its mass to the radius of its focal horizon. It is mentioned that while there may be a focal point, it is difficult to accurately describe the effect in a formula due to the uneven distribution of mass in gravitational lensing. The conversation ends with the speaker expressing gratitude for finding the information they were looking for.
scupydog
Does a gravitational lense have a focal point, like a nomal lense but as a focal point sphere/horizon. if so is there a formula that relates the mass of the GL with the radius of its focal horizon. Happy xmas.

I would imagine it does, but no-one has bothered to make a formula to describe it seeing as gravitational lensing isn't caused by a nice uniform lense, but by an uneven body of mass, so it would be very difficult to describe the exact effect in a formula.

Thx for reply, i think i have found what i was looking for

## What is a gravitational lens?

A gravitational lens is a phenomenon in which the gravitational field of a massive object, such as a galaxy or a cluster of galaxies, bends and distorts the path of light coming from a more distant object behind it. This results in the formation of multiple images of the distant object, creating a "lens-like" effect.

## What is the focal point of a gravitational lens?

The focal point of a gravitational lens is the point at which the multiple distorted images of a distant object converge. This is determined by the mass and distribution of the lensing object, as well as the distance and position of the distant object.

## What is the mass-radius formula for a gravitational lens?

The mass-radius formula for a gravitational lens is a mathematical equation that relates the mass and radius of the lensing object to the angle of deflection of light passing through it. This formula is used to calculate the mass of the lensing object based on the observed deflection of light.

## How is a gravitational lens used in astronomy?

Gravitational lenses are used in astronomy to study and measure the mass distribution of massive objects, such as galaxies and galaxy clusters. They also provide a way to study distant objects that would otherwise be too faint or small to be observed directly.

## Can gravitational lenses be used to study dark matter?

Yes, gravitational lenses are one of the primary methods used to study dark matter, which is a type of matter that does not emit or reflect light and is therefore invisible to traditional telescopes. By analyzing the effects of gravitational lenses on the light passing through them, scientists can make inferences about the distribution and properties of dark matter in the universe.

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