Diagram above shows a ray of light moving from air toliquid A. Find the refractive index of the liquid A.

**Answer:**

Angle of incident, i = 90o - 30o = 60o

Angle of refraction, r = 45o

Refractive index,

\begin{gathered}
n = \frac{{\sin i}}
{{\sin r}} \hfill \\
n = \frac{{\sin 60^o }}
{{\sin 45^o }} = 1.22 \hfill \\
\end{gathered}