The phenomenon of bending of light caused by gas density variations in the atmosphere is called:

1. The atmosphere has layers of different temperature and density. 2. Different densities mean different refractive indices. 3. Light therefore bends as it passes through changing layers. 4. This bending is called atmospheric refraction. 5. It causes twinkling stars, advanced sunrise, and delayed sunset. 6. So the phenomenon is atmospheric refraction. _Source: syllabus Science Ch 11 'Human Eye and the Colourful World'_