What is refresh rate?
Introduction
A monitor's refresh rate, or vertical scan rate, is the number of times in a second a monitor redraws a picture
CRT monitors and refresh rate
Refresh rate is an important attribute of cathode ray tube (CRT) monitors and any sort of cathode ray display because of the way the CRT renders the image. The glass in the screen is coated with phosphors. The CRT draws the image by shooting electron beams at the glass, electronically exciting the phosphors until they glow. The beam continues to scan left to right, descending one pixel each cycle, until it reaches the bottom. Then it returns to the top and starts again.
The phosphors, once glowing, will start to fade after the electron beam passes. This is the reason the CRT redraws the whole image instead of just the parts that change. The higher the refresh rate, the less this fade will be apparent, as the phosphors won't have as much time to dim between refreshes.
The lower the rate, the more apparent the fade will be. The "flicker" you see is the repeated brightening and dimming of the phosphors. When the refresh rate is high enough, you will no longer perceive the flicker.
Most people stop perceiving flicker at refresh rates of about 75Hz (75 screen redraws per second). Some people need refresh rates in the 80s. Refresh rates in the low 60s hurt most people's eyes.
To change your refresh rate settings, follow the instructions in the Knowledge Base document
What should I do if my monitor display flickers or
wavers?
LCD monitors and refresh rate
Refresh rate does not apply to LCD (liquid crystal display, now commonly referred to as flat panel) monitors, because they do not render images the same way CRT monitors do. Pixels in LCD monitors remain open or closed as needed until the image changes, and the light that passes through from behind stays constant. Therefore, the pixels don't fade. The rate that affects LCD displays is "response time", the time it takes for a pixel to go from fully open (the brightest intensity) to fully closed (black). Response time is a fixed property, not a configurable setting.
In Windows, Display Properties includes settings for refresh rate, but they are only there for compatibility with the video card, which must be able to handle a CRT that can do multiple rates. An LCD monitor has only one optimal refresh rate setting, so it expects a specific value. Changing this setting for an LCD monitor will affect the image (e.g., it may shift it off center), but will not affect the monitor's actual refresh rate.