Atmospheric refraction tends to diminish the effect of earth curvature by approximately _______ per cent.

• A. 16
• B. 14
• C. 18
• D. 20

Answer: (B)

This questions centers on how atmospheric refraction changes the appearance of the Earth's curvature. Refraction bends light downward as it moves through the atmosphere, which makes distant points on the horizon look higher and farther away than their true geometric positions. That downward bend effectively flattens what we would normally see from curvature, so the apparent dip or drop caused by the Earth’s curvature is reduced.

In surveying practice, this flattening is accounted for with a typical rule of thumb: the curvature effect is diminished by about fourteen percent. In other words, if the geometric drop due to curvature at a certain distance would be D, the observed drop under average atmospheric conditions is about 0.86 × D. This 14% figure reflects an average effect under common conditions and explains why the correct choice is the approximate value used in practice. The exact amount can vary with temperature, pressure, and humidity, but fourteen percent is the standard estimate for general calculations.