Jet engines work on the principle of Newton's law of action and reaction. According to this principle, for every action, there is an equal and opposite reaction. In the case of a jet engine, the action is the expulsion of high-velocity exhaust gases from the rear of the engine, and the reaction is the forward thrust that propels the aircraft.

How a Jet Engine Works:
1. Air Intake: The jet engine draws in a large amount of air through an intake. This intake is designed to compress the incoming air and direct it into the engine.

2. Compression: The air is then compressed by multiple stages of rotating compressor blades. This compression increases the pressure and temperature of the air, creating a high-energy airflow.

3. Combustion: Fuel is injected into the compressed air and ignited. The burning fuel rapidly expands, releasing an enormous amount of energy. This energy causes the temperature and pressure of the gases to increase significantly.

4. Exhaust: The high-pressure and high-temperature gases from the combustion process are forced out through the rear of the engine at a high velocity. This expulsion of gases creates a reaction force in the opposite direction, pushing the aircraft forward.

Newton's Law of Action and Reaction:
Newton's third law states that for every action, there is an equal and opposite reaction. In the case of a jet engine, the action is the expulsion of high-velocity exhaust gases, and the reaction is the forward thrust that propels the aircraft. The force exerted by the gases leaving the engine is equal in magnitude but opposite in direction to the force propelling the aircraft forward.

Conclusion:
In conclusion, the principle on which a jet engine works is Newton's law of action and reaction. The engine intakes air, compresses it, combines it with fuel, and ignites it to create high-pressure and high-temperature gases. The expulsion of these gases at a high velocity creates a reaction force that propels the aircraft forward.