The superposition of two waves is given by $$\sin(\omega_1 t)+\sin(\omega_2 t)=2\cos\left(\frac{\omega_1-\omega_2}{2}t\right)\sin\left(\frac{\omega_1+\omega_2}{2}t\right).$$ For sound waves, this effect is perceived by the human ear as beats.

Does the human eye perceive a similar effect for electromagnetic waves? Is it possible to produce visible light through the superposition of two microwaves?