The main difference between mechanical and electromagnetic waves is as follows: mechanical waves need a substance such as a liquid to travel through. Electromagnetic waves, on the other hand, do not need any substance or medium to travel through. Electromagnetic waves are transmitted in a vacuum while mechanical waves are not transmitted in a vacuum. As mentioned above, mechanical waves travel in a substance or medium such as water. An example of mechanical waves is when a stone is thrown into the water. The resulting ripples are mechanical waves. Examples of electromagnetic waves are light waves or radio signals.