Is it possible for two physical quantities to have the same units and why

Nopes,Example:-thrust and weight both represent the force. So they will have same unit.

in simple terms, the principle states that the buoyancy force on an object is equal to the weight of the fluid displaced by the object, or the density of the fluid multiplied by the submerged volume times the gravitational acceleration, g. this is also known as upthrust.

so easy. just google the electromagnetic waves and it’ll pop up.