- #1

Suraj M

Gold Member

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## Homework Statement

This is how my teacher dictated the question...

---A layer of oil 3 cm thick is floating on a layer of coloured water 5 cm thick, the RI of the coloured water with respect to the oil is ##\frac{5}{3}##. The apparent depth of the liquid is ##\frac{36}{7} cm##. What is the RI of oil(with respect to air).

## Homework Equations

##d' = \frac{d}{n}##

n is RI

## The Attempt at a Solution

This is what my teacher told us to do, after we tried to do it.

$$\frac{36}{7} = \frac{d_{oil}}{n_{oil ~w.r.t~ air}} + \frac{d_{water}}{ n_{water~ w.r.t~ oil}}$$

solving this we get ##n_{oil} = \frac{7}{5}##

I have a feeling this is wrong, though my teacher says it is right.

Particularly in the place where we use ##n_{water ~wrt~ oil}## wouldn't this actually mean that the level of water is being viewed from the oíl. Which is not the case.

I thought maybe if we took ##n_{water ~wrt~ air}## we might get the answer but i'm starting to think., even that won't give me the answer.

could you point me in the right direction..

thank you