The phenomenon of objects appearing to waver when viewed through a turbulent hot air stream is primarily due to variations in the air's refractive index.

Atmospheric Refraction Explained

Hot air is less dense than the surrounding cooler air. Light travels at different speeds through air of different densities. This difference in speed causes light rays to bend, a process known as refraction.

Turbulence and Light Bending

• In a turbulent hot air stream, the air density is constantly changing and swirling.
• As light rays from an object pass through these pockets of varying density (hotter, less dense air and cooler, denser air), they bend unpredictably.
• This rapid and irregular bending of light causes the image of the object to shift and appear distorted or wavering.

Why It's Refraction

This effect is a specific instance of atmospheric refraction, occurring on a small scale due to the localized temperature and density gradients within the turbulent air. Options like dispersion (splitting of light into colors) or diffraction (bending around obstacles) do not explain the characteristic shimmering or wavering seen here.

Conclusion

Therefore, the wavering observed is best described as small-scale atmospheric refraction caused by the turbulent mixing of air with different temperatures and densities.