Consider the picture in Fig 1 In which direction will the wa

Consider the picture in Fig: 1. In which direction will the water droplets move, towards the air-water boundary or away from it? In which direction will the air bubbles move, towards the air-water boundary or away from it? We can think of the electrons behaving as water droplets. Since holes are missing electrons, they can be thought of as the bubbles i.e. missing water. Consider an electron in the depletion region of the p-n junction. For the electron to lower its energy, which way would it move (left or right)? Considering the hole is a missing electron, for the system to lower its energy which way will the hole move (left or right)?

Solution

1. It is the half filled vertical fish tank. The water shall move downwards to Air-water boundary due to gravity and the droplets being heavier than air.

2.  The air bubble shall move upwards to Air-water boundary due to bubbles being lighter than water.