Illusions questions

Mona Lisa is famous for an optical illusion aka 'the mysterious smile'. The illusion is caused due to peripheral vision as the focus of the viewer shifts from the eyes of the portrait to the lips of the portrait.

There are two illusions associated with the Ames Room. First the room appears cubic when viewed monocularly from a special viewing point (the true shape of the room is trapezoidal). Secondly, within an Ames Room people or objects can appear to grow or shrink when moving from one corner to the other.

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.

The effect is similar to irisation. Iridescent clouds are a diffraction phenomenon caused by small water droplets or small ice crystals individually scattering light. Larger ice crystals do not produce iridescence, but can cause halos, a different phenomenon.

This is Australia map, with north at the bottom side.

In this scintillating grid illusion, dark dots seem to appear and disappear randomly. Various theories have been proposed to explain it. It may be caused by the mechanism of lateral inhibition (the capacity of an excited neuron to reduce the activity of its neighbors).

This is known Ebbinghaus illusion. Although commonly thought of as an illusion of size, recent work suggests that the critical factor in the illusion is not the size, but the distance of the surrounding circles. In a similar way, the Moon appears larger on clear sky when it's close to the horizon line.

A Hybrid Image is an optical illusion developed at MIT in which an image can be interpreted in one of two different ways depending on viewing distance. In order to see Marylin clearly, you need to move away of the screen

In this Ehrenstein illusion the sides of a square placed inside a pattern of concentric circles take an apparent curved shape. But in reality, the sides are straight.

Both shapes are the same, but the bottom one is placed more to the right. This is however difficult to notice. It is known as Jastrow Illusion.