The monitor ripples slightly - what could be the problem?

Question

Monitors

Good afternoon.
The problem is this - if you look closely, the monitor slightly ripples - it's hard to see, but you can. Because of this, the eyes hurt.
I connected the monitor to the laptop - there is no ripple.
What is the problem, in the cable that goes to the system unit and there is interference due to other wires, or because of the video card?