# What gas law is illustrated by this picture?

Boyle's Law states that pressure and volume of a gas are inversely proportional ($P \cdot V$ is constant for constant mols of ideal gas and constant temperature).
As the piston is lowered to a new volume $\frac{1}{2}$ the original, the volume the gas occupies decreases by that same factor, however, the particles are colliding with each other and the walls of the container more often, resulting in a greater pressure. The pressure increases by a factor of 2, and $P \cdot V$ is constant.