# JEE Main & Advanced Physics Ray Optics Refraction Through a Glass Slab

Refraction Through a Glass Slab

Category : JEE Main & Advanced

(1) Lateral shift : The refracting surfaces of a glass slab are parallel to each other. When a light ray passes through a glass slab it is refracted twice at the two parallel faces and finally emerges out parallel to it's incident direction i.e. the ray undergoes no deviation $\delta =0$ The angle of emergence (e) is equal to the angle of incidence (i)

The Lateral shift of the ray is the perpendicular distance between the incident and the emergent ray, and it is given by

$\mathbf{MN = t sec r sin (i - r)}$

(2) Normal shift : If a glass slab is placed in the path of a converging or diverging beam of light then point of convergence or point of divergence appears to be shifted as shown

Normal shift

$OO'=x=\left( 1-\frac{1}{\mu } \right)\,t$

(3) Optical path : It is defined as distance travelled by light in vacuum in the same time in which it travels a given path length in a medium.

Time taken by light ray to pass through the medium $=\frac{\mu \,x}{c}$; where $x=$ geometrical path and $\mu x=$ optical path

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