The formula to calculate the Prism Refraction Angle (PRA) is:
\[ PRA = AOI + AOE - AOD \]
Where:
Let's say the angle of incident (AOI) is 30 degrees, the angle of emergence (AOE) is 40 degrees, and the angle of deviation (AOD) is 10 degrees. Using the formula:
\[ PRA = 30 + 40 - 10 = 60 \text{ degrees} \]
So, the prism refraction angle is 60 degrees.