Dark matter lensing & the photons: It’s the characteristics of light because of which the existence of dark matter can be proven along with the presence of the celestial matter AROUND.
Thus the phenomenon is so-called Gravitational lensing. It is referred for the distribution of the celestial matter cluster of galaxies between a distant light source and an observer, that is capable of bending the light from the source as the light travels towards the observer. It is a phenomenon based upon the focal lens & not optical lens
a gravitational lens produces a maximum deflection of light that passes closest to its center, unlike the optical lens.
Optical lens: A lens is a transmissive optical device that focuses on or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (elements), usually arranged along a common axis.]
Gravitational lensing has no single focal point
Henry Cavendi in 1784 (in an unpublished manuscript) and Johann Georg von Soldner in 1801 (published in 1804) had pointed out that Newtonian gravity predicts that starlight will bend around massive objects had already been supposed by Isaac Newton in 1704 in his Queries No.1 in his book Opticks. The same value as Soldner’s was calculated by Einstein in 1911 based on the equivalence principle alone. However, Einstein noted in 1915, in the process of completing general relativity, that his (and thus Soldner’s) 1911-result is only half of the correct value. Einstein became the first to calculate the correct value for light bending. The term “lens” in the context of gravitational light deflection was first used by O.J. Lodge, who remarked that it is “not permissible to say that the solar gravitational field acts like a lens, for it has no focal length.
Over the last few months, I am following some space programs on this subject and came across the word Copernican revolution. We are in the 4th stage of the same and big thanks to the Astronauts, scientists, and engineers who have created The Arecibo Observatory is a radio telescope in the municipality of Arecibo, Puerto Rico.
Gravitational lenses act equally on all kinds of electromagnetic radiation, not just visible light.