Question

A fish looking up through the water sees the outside world containing in a circular horizon. If the fish is 28 cm below the water surface, the radius of that circle is?
$(R.Iofwater=\frac{4}{3})$

• A. 12 cm
• B. 14 cm
• C. $12\sqrt{7}cm$
• D. $28\sqrt{7}cm$

Answer 1

The correct option is C $12\sqrt{7}cm$

$r=\frac{h}{\sqrt{{\mu }^2-1}}=\frac{28}{\sqrt{\frac{4^2}{3^2}-1}}=\frac{28}{\sqrt{\frac{16}{9}-1}}=\frac{3\times 28}{\sqrt{7}}=12\sqrt{7}cm$