PhysicsChapter 5: Optics
Gravitational Lensing (textbook Level)
Introduction
Gravitational lensing is the bending of light due to the gravitational effect of a massive object. According to modern physics, massive objects curve spacetime, and light follows paths through this curved spacetime.
Definition
Gravitational Lens
A massive object such as: * a galaxy; * galaxy cluster; * massive compact object can act like a gravitational lens.
What We Observe
Depending on the alignment between observer, lensing object, and distant source, gravitational lensing can produce: distorted images; multiple images; * arcs; rings; magnification.
Einstein Ring
If the source, gravitational lens, and observer are very closely aligned, the distant object's image can form a ring called an **Einstein ring**.
Why It Is Useful
Astronomers use gravitational lensing to: * study very distant galaxies; * estimate mass in galaxies and clusters; * investigate dark matter; * detect some objects that are otherwise difficult to observe.
Important Distinction
A gravitational lens is not made of glass. It works because gravity changes the path followed by light.
Exam preparation
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Review the key facts, formulas and checks before you move on.Gravitational Lensing (textbook Level)
Sticky Notes · Quick Revision
GRAVITY
- Bends light path
EINSTEIN RING
- Strong alignment
USE
- Mass + distant objects
60-second revision
- Massive object → bends light path.
- Can produce arcs/rings/multiple images.
- Useful in astronomy.
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