The main difference between reaction and impulse turbine is 
that reaction turbine operates on newtons third law of 
motion that is when steam leaves the rotor blades at an  
angle the turbine is pushed towards opposite direction and 
to a certain extent static pressure impulse is also 
utilised for the movement.
Where as in impulse turbine only kinetic head of steam is 
responsible for movemement of turbine.that is movement of 
turbine takes place in direction of impact and not opposite 
to the impact as was the case with reaction turbines.