As I push down the plunger on a sealed syringe, the pressure begins to

push back against me. Who's law is this?

Boyle's Law

Charles' Law

Gay-Lussac's Law

Avogadro's Law

Boyle's Law

Explanation:

This is a simple Boyle's law at work in this scenario.

Boyle's law is one of the gas law and it states that "The volume of a fixed mass of gas varies inversely as the pressure changes if temperature is constant".

This law was proposed by Robert Boyle.

In a sealed syringe, the volume of gas begins to decrease as the plunger is pressed. Conversely, it becomes harder to press due to increasing pressure in the tube. The pressure pushes back the more it is applied. We can see that the higher pressure applied, the lower the volume of the gas.

This is clear cut practical of the Boyle's law.