10 most difficult optics riddles

The Fata Morgana occurs because rays of light are bent when they pass through air layers of different temperatures in a steep thermal inversion, where an atmospheric duct has formed. It significantly distorts the object on which it is based, often such that the object is completely unrecognizable. The Fata Morgana may be seen on land or at sea, in polar regions, or in deserts. It may involve almost any kind of distant objects, including boats, islands, and the coastline.

Mantis shrimps, or stomatopods, are marine crustaceans of the order Stomatopoda. They are thought to have the most complex eyes in the animal kingdom and have the most complex visual system ever discovered. Compared to the three types of photoreceptor cells that humans possess in their eyes, the eyes of a mantis shrimp have between 12 and 16 types of photoreceptors cells. Furthermore, some of these shrimp can tune the sensitivity of their long-wavelength colour vision to adapt to their environment.

Bokeh has been defined as "the way the lens renders out-of-focus points of light". It can be good or unpleasant, depending on the lens aberrations and aperture shape. The term comes from Japanese for "blur".

A rainbow is a meteorological phenomenon that is caused by reflection, refraction and dispersion of light in water droplets resulting in a spectrum of light appearing in the sky. It takes the form of a multicoloured circular arc. Rainbows caused by sunlight always appear in the section of sky directly opposite the sun.

Halo is the name for a family of optical phenomena produced by light interacting with ice crystals suspended in the atmosphere. Halos can have many forms, ranging from colored or white rings to arcs and spots in the sky. Among the best known halo types are the circular halo (properly called the 22° halo), Other common optical phenomena involving water droplets rather than ice crystals include the glory and the rainbow.

Rayleigh scattering, named after the British physicist Lord Rayleigh (John William Strutt), is an elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the radiation.

Man is usually sensitive to about 500,000 colors. Tetrachromacy is the condition of possessing four independent channels for conveying color information, or possessing four types of cone cells in the eye. Organisms with tetrachromacy are called tetrachromats which can see up to 99 million shades.

A Brocken spectre or mountain spectre, is the apparently enormous and magnified shadow of an observer, cast upon the surfaces of clouds opposite the sun. The head of the figure is often surrounded by the glowing halo-like rings of a glory—rings of coloured light that appear directly opposite the sun when sunlight meets a cloud of uniformly-sized water droplets. The phenomenon can appear on any misty mountainside or cloud bank.

A Satellite flare (also called a Iridium flares ) is a phenomenon caused by man-made satellite where the sunlight is reflected back to Earth. This results in a quick and bright "flare." Some flares can be up to 20 times brighter than Venus. These can be very bright. So much so, that it can even be seen during the day.

Such shallow depth-of-field is possible with lens of large aperture size (small f-number). The large aperture is a typical feature (and advantage) of a fixed focal length lens. The photo was taken with a 50mm f/1.4 lens.