Question

Take a bright metal ball and make it black with soot in a candle flame. Immerse it in water. How does it appear and why? (Make hypothesis and do the above experiment)

Answer 1

1. If a metal ball coated with soot of candle flame is immersed in water, then it appears shining.
   
2. Soot is non-stick to water. A thin air film is formed in between water and soot as shown in the figure.
3. The light ray is travelling from water(denser medium) to air(Rarer medium).
   
4. The angle of incidence is greater than the critical angle, total internal reflection takes place.
   
5. As the ray reflects at water air interface, the metal ball appears shining.
   
6. It is similar to shining of air bubble in water.