What is gravitational lensing?

Question

Could someone provide a link? With diagrams, too. Thanks.
While you are at it, what on earth is a quasar and why can it be used for gravitational lensing?

Answer 1

Gravitation lensing is when light passes close enough to a black hole to be bent by gravity and get focused like it would if it were bent by the glass in a lens. Can't help you the diagram though, sorry. A quasar can be used for gravitation lensing because it has a black hole at its center.

Answer 2

One important consequence of the influence of Einstein's gravitation on light is that gravitational masses can alter the direction of light and cause lensing effects.
In a gravitational lens, the gravity from the massive object bends light, but unlike an optical lens maximum 'bending' occurs closest to, and minimum 'bending' furthest from, the center of the lens.Consequently a gravitational lens has no single focal point.

Imagine a bright object such as a star, a galaxy, or a quasar, that is very far away from Earth.If there is nothing between it and us, we see one image of the quasar. Yet, if a massive galaxy (or cluster of galaxies is blocking the direct view to the quasar, the light will be bent by the gravitational field around the around the galaxy and we will see twin images of the quasar. This is what is called "gravitational lensing," since the intervening galaxy acts as a lens to focus the image of the distant quasar to a new location

Answer 3

Gravitational lensing is the displacement of light due to the warping of space by a gravitational lens (a massive object in space that bends light that passes by it, due to the gravitational forces). GRAVITY Gravity is a physical force that pulls objects together. Every bit of mass produces a gravitational force; this force attracts all other masses. The more massive an object, the stronger the gravitational force. Newton formulated the laws of gravity.

Answer 4

Here is an awesome Hubble telescope photo of a gravitational lens

http://hubblesite.org/gallery/album/entire_collection/pr2006023a/

Caused by a galaxy in front of a group of quasars, the
lens effect caused 5 distinct images of the quasars to appear radially around the center.
Follow the information about the photo and it will enlighten you.

Answer 5

The bending (and thus focussing) of light by gravitational fields is called gravitational lensing. You can get more information on this topic through an internet search. Sites related to astronomy will be the ones to look for.