# Problem doing glass slab refraction based questions

## Homework Statement

I understand the basic formula per say of the apparent shift due to glass slab (t(1-1/u)) But when a question comes on i just don't know how to proceed. For ex this question came on my test and i just couldn't visualise how to make ray diagram or even attempt it.

## Homework Equations

'"There is a dust particle on a a glass slab of thickness t and refractive index 3/2 . When seen from one side if the slab, the dust particle appears at a distance 6 cm. From the other side it appears at 4cm. Find the thickness t of the glass slab"

## The Attempt at a Solution

t(1-1/3/2)

Simon Bridge
Homework Helper
'"There is a dust particle on a a glass slab of thickness t and refractive index 3/2 . When seen from one side if the slab, the dust particle appears at a distance 6 cm. From the other side it appears at 4cm. Find the thickness t of the glass slab"
... I think you mean that the dust particle is inside the glass slab.

The particle is closer to one side than the other.

sketch the slab side on - put a dot in it closer to one side than the other.
draw a line perpendicular to the sides of the slab that goes through the dot.
Where the line intersects the sides of the slab is points A and B.
The dot is point P.

All these are real, rather than apparent, positions.
t=|AB|