Why does the sooted iron ball shine when immersed in water?
Answer: Dipping a sooted iron ball in water makes the ball shine. Because the ball is smeared with soot, a thin layer of air adheres to the ball. Light rays pass from a denser medium to a lighter medium as they pass from the water to the air layer. As a result, rays whose angle of incidence is greater than the critical angle of water and air are fully reflected. When those reflected rays reach the eye, the ball appears brighter.