Snell’s law states that when light enters obliquely into a transparent medium from another transparent medium, then for a fixed pair of media and for a fixed colour of light the ratio of the sine of the angle of incidence to the sine of the angle of refraction always remains constant.
Infrared light comes of TV remote control which cannot be seen with the naked eye.
The wavelength of visible light is between 400 nm to 700 nm.
The imaginary plane which passes through the principal focus of a lens, perpendicular to its principal axis is called the focal plane of the lens.
Total internal reflection is the phenomenon that occurs when a propagated wave strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal surface of the medium.
In a curved mirror, the middle point of the reflecting surface is called the pole of the mirror.
A refractive medium enclosed by two curved surfaces is called lens.
Mirror is a polished or smooth surface that forms images by reflection.