ATMOSPHERIC LENSING

Because of refractive index variations in the air layers just above the ground, atmospheric lensing may significantly deform our view of distant Earth-objects. Similarly, gravitational lensing perturbs our view of the distant Universe and affects our physical understanding of various classes of extragalactic objects. After recalling the basic principles underlying the formation of atmospheric and gravitationally lensed mirages, we describe a simple optical lens experiment which accounts for all types of image configurations observed among presently known gravitational lens systems...

English version :

Atmospheric Lensing

Version française :

Les mirages atmosphériques

GRAVITATIONAL LENSING

During the elaboration of his theory of General Relativity, Einstein (1915) predicted that a massive object curves the spacetime in its vicinity and that any particle, massive or not (cf. the photons), will move along the geodesics of this curved space...

English version :

Gravitational Lensing

Version française :

Les mirages gravitationnells

THE OPTICAL GRAVITATIONAL LENS EXPERIMENT

For didactical purposes, it is very useful to construct and use optical lenses that mimic the deflection of light rays...

English version :

The Optical Gravitational Lens Experiment

Version française :

Phénomène de lentille gravitationnelle

OTHER EXAMPLES OF CAUSTICS AND MULTIPLE IMAGING

1. Gravitational lensing and the wine glass experiment 1. Gravitational lensing and the wine glass experiment

The formation of multiple images of a distant quasar by the gravitational lensing effects of a foreground galaxy may be very simply, and faithfully, accounted for by the wine glass experiment described below.

2. Multiple imaging as seen by whales and sharks

The interface between the air and the water in a swimming pool, on a lake, on a sea, etc., is wavy and as a result, the propagation of light rays from a distant source (cf. the sun, the moon, etc.) gets distorted after entering water...

3. Multiple imaging at the House of Mirrors

Finally, it is fun to observe multiple images of human beings at the House of Mirrors, available during most of the big city fairs. Such mirages are produced by curved mirrors which distort light rays emitted from the surroundings.

Version française :

Les lentilles gravitationnelles et l'expèrience du verre de vin

English version :

Other Examples of Caustics and Multiple Imaging