Lateral Shift – Note Class 11

Lateral Shift

When a ray of light incident on a glass slab then emergent ray coming out of the slab will be parallel to initial direction of incident ray.

The Perpendicular distance between emergent ray and initial direction of incident ray is called Lateral Shift.

It is denoted by delta “δ” .


                                 Let us consider a ray of light AB incident on glass slab PQRS having thickness “t” . It is refracted along BC and finally emerges along “CD” as shown in given diagram. lateral shift

let, i = angle of incidence

r= angle of refraction

Here CM = δ is lateral shift.

Now From triangle ‘BCM,’ we have


or, CM= BC sin(i-r)

or, δ= BC sin (i-r)………..(i)

Again From triangle ‘ BEC ‘ we have


or, Cos r= PS/BC      (here, BE= PS)

or, Cosr = t/BC

or, BC= t/cosr ……………   (ii)

From equation (i) and (ii) , we get

δ= Bc sin(i-r)

Lateral Shift

 Hence  this equation shows that lateral shift increase with increase in angle of incidence .






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