Lights

Optical illusions are visuals that tend to be deceptive to the eye and brain.

The blind spot in our eyes is a tiny functional area about the size of a pinhead, where the optic nerve passes through the surface of the retina. This area has no photoreceptor cells that detect light, which creates the blind spot 

Two eyes give us a wider field of vision. It also helps us perceive the depth which forms a 3D impression and enhances the ability of assessing distinct position of object.

Binocular vision is a vision formed by using two eyes where there is an overlapping field of view.

When light travels from one medium to another, the speed of its propagation changes, as a result, it ‘bends’ or is ‘refracted’. Now when light passes through a prism, it is refracted towards the base of the triangle.

When there is no water in the glass, the light from the coin experiences very little refraction and we can see the light from the penny. When there is water in the glass, the light from the coin experiences refraction (bending) and reflection (total internal reflection, TIR) such the light it is not able to reach the observer’s eyes. A small amount of refraction occurs as the light leaves the coin and travels through the bottom of the glass, then refraction occurs again as it enters the water. When refraction occurs at the side of the glass there is Total Internal Reflection because of the angle of incidence. The light ends up traveling at such an angle that we are unable to see the coin.

Total internal reflection is the phenomenon which occurs when the light rays travel from a more optically denser medium to a less optically denser medium.

Fermat's principle states that “light travels between two points along the path that requires the least time, as compared to other nearby paths.” From Fermat's principle, one can derive (a) the law of reflection [the angle of incidence is equal to the angle of reflection] and (b) the law of refraction [Snell's law].

When a ray of light travels from one medium to another medium, it changes its path because it has different speed in different media. This phenomenon is called refraction of light.

When light passes from one medium to another, say air, a glass of water, then a part of the light is absorbed by particles of the medium, preceded by its subsequent radiation in a particular direction. This phenomenon is termed a scattering of light. The intensity of scattered light depends on the size of the particles and the wavelength of the light.