The lob sends the ball in a high arc over the opponent, landing deep in the back court. 

Trajectory Optimization 
The maximum height depends on the square of the initial speed and the square of the sine of the launch angle, divided by twice the gravitational acceleration. The horizontal range depends on speed squared times the sine of double the launch angle, divided by gravity. The ball must clear the opponent (~2 m+) while landing near the back wall within court length (~9.75 m). 

Energy Conservation 
Kinetic energy converts to potential energy on the way up and back during descent. Air resistance requires slightly higher initial velocity than the frictionless ideal.