The deeper the diver takes the helium balloon, the more it reduces in size. This is due to the pressure of the water column above pressing on the balloon. According to Boyle’s law (P= k*1/V.), as the volume of the balloon decreases, the pressure of the helium inside increases.
As the water vapor touches the mirror the particles of the vapor loses energy and they move less then the process Condensation takes place in which the gas turns into water.
