Question

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what is lens and What is glass slab​

Answer 1

Answer:

Hii Mate,

Lens

A transparent medium, bounded by two surfaces, of which at least one is spherical.

Glass Slab.

Glass slab is a cuboidal piece of glass..

Answer 2

Answer:

A lens is transparent reflecting medium with one plane and one spherical surface

or

When a ray light is passing from air to glass, that is, from a rarer medium to a denser medium, the refracted ray bends towards the normal drawn at the point of incidence. ... The emergent ray, O1E which is nothing but the refracted ray emerging out of the glass slab is parallel to the incident ray.