Consider the situation in figure. The bottom of the pot is a reflecting plane mirror, S is a small fish and T is a human eye. Refractive index of water is.
  1. At what distance(s) from itself will the fish see the image(s) of the eye?
  2. At what distance(s) from itself will the eye see the image(s) of the fish.
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  1. Let x = distance of the image of the eye formed above the surface as seen by the fish
So, $\frac{\text{H}}{\text{x}}=\frac{\text{Real depth}}{\text{Apparent depth}}=\frac{1}{\mu}$ or $\text{x}=\mu\text{H}$

So, distance of the direct image $=\frac{\text{H}}{2}+\mu\text{H}=\text{H}\Big(\mu+\frac{1}{2}\Big)$

Similarly, image through mirror $=\frac{\text{H}}{2}+(\text{H}\times\text{x})=\frac{3\text{H}}{2}+\mu\text{H}=\text{H}\Big(\mu+\frac{3}{2}\Big)$
  1. Here, $\frac{\frac{\text{H}}{2}}{\text{y}}=\mu,$ So, $\text{y}=\frac{\text{H}}{2\mu}$
Where, y = distance of the image of fish below the surface as seen by eye.

So, Direct image $=\text{H}+\text{y}=\text{H}+\frac{\text{H}}{2\mu}=\text{H}\Big(1+\frac{1}{2\mu}\Big)$

Again another image of fish will be formed $\frac{\text{H}}{2}$ below the mirror.

So, the real depth for that image of fish becomes $\text{H}+\frac{\text{H}}{2}=\frac{3\text{H}}{2}$

So, Apparent depth from the surface of water $=\frac{3\text{H}}{2\mu}$

So, distance of the image from the eye $=\text{H}+\frac{3\text{H}}{2\mu}=\text{H}\Big(1+\frac{3}{2\mu}\Big).$
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