Question

Explain why a test tube immersed at a certain angle in a tumbler of water appears to have a mirror surface for a certain viewing position?

Answer 1

1. The glass acts as a denser medium and air in the test tube acts as a rarer medium.
   
2. As light tries to enter the air in the test tube it undergoes total internal reflection bouncing back into the water from the surface of the test tube, i.e., When rays of light travel through water strikes the water glass interface of the test tube at an angle which is more than a critical angle for water. Then the light ray suffers total internal reflection.
   
3. When these reflected rays reach the eye, they appear to come from the surface of the test tube itself.
   
4. So the test tube appears as it has a mirror surface