Draw a ray diagram of refraction of light in a glass slab.

The refractive index of a material can be understood as a dimensionless number that describes how fast light travels through the material (here say, glass). It is defined as n = c v Where c is the speed of light in vacuum and v is the phase velocity of light in the medium. Through a glass slab, the light before coming back to the air suffers refraction two times. At the second time, the refracted ray bends away from the normal. If the light is incident at right angles then it will pass through the glass slab without any deviation. The ray diagram of refraction of light in a glass slab is as follows:

Draw ray diagram for image formation by concave lens when the object is placed between infinity and optical centre ‘O’.

The image formed by a concave lens when the object is kept between infinity and optical center 'O' is virtual in nature, erect and diminished, and on the same side of the lens as the object. The image formed is between focus F1 and optical center' O'.

Write the definition of the refractive index of a medium.

The Refractive index of a medium can be defined as the ratio of the speed of light in a vacuum to a particular medium. It is also called the index of refraction. It is considered to be a dimensionless quantity describing how light travels in any medium.