source: here
3. Refresh rates
Some users might find that they are able to discern a flickering effect when they look at their monitor. This effect is due to the way that the display on a monitor refreshes itself. As the refresh rate of a monitor is so high (the default setting within MS Windows is usually 100Hertz) it is usually impossible to see the flicker under normal circumstances however some refresh rates may cause problems particularly with fluorescent lighting. Fluorescent lights usually have a flicker rate at a multiple of the mains frequency (50-60Hz or 2X) and so if your monitor refresh rate is set within the ranges 50-60Hz or 100-120Hz, the effect of the lights and your monitor refreshing at the same frequency may mean that you may be able to discern a flickering effect. To combat this using, a refresh rate that is not a multiple of mains frequency will mean that the lights and monitor refresh at different rates thus making the flicker less noticeable.
To change the refresh frequency for your monitor, access the display properties by right-clicking on an empty part of the Windows desktop, and choose Properties from the menu. When the display properties panel is shown, go to the Settings tab and click the Advanced button which will open a new advanced settings window. In the advanced settings window, click on the Monitor tab. Or, you can also access these display properties through the Control Panel:
Start Menu > Settings > Control Panel > Display > Settings tab > Advanced button > Monitor tab