Question

Why emergent ray is not observed from the adjoining surface when angle of incidence is very small???

Answer 1

When a ray of light passes through a slab of transparent medium, its gets laterally shifted . This is called lateral displacement .

The lateral displacement is given by -

d = [t * sin(i - r)/cosr

where, t = width of glass slab

           i = angle of incidence

           r  =  angle of refraction

Here, when angle of incidence is very small we assume it is very close to 0 degree . So, angle of refraction is also very small , we can say that close to zero degree .

So, value of (i - r) is close to 0 degree .

=>  value of sin(i - r) is close to zero .

=> value of lateral displacement ,d is close to zero .

So, lateral shift is very very small or negligible .

Thus, we cannot differentiate between incident ray and emergent ray .

So, emergent ray is not observed from the adjoining surface when angle of incidence is very small .