When the burner of a stove turns red, it's an indication that it has reached a high temperature, usually in the range of several hundred degrees Celsius (over 500 degrees Fahrenheit). The red color is a result of incandescence, which occurs when a material is heated to a temperature where it emits visible light.
The burner of a stove is typically made of metal, such as iron or steel, and is coated with a material that can withstand high temperatures, such as porcelain or enamel. When the burner is turned on and heat is applied, the metal absorbs the energy from the flame or electric heating element, causing its temperature to rise rapidly.
As the temperature of the metal increases, it begins to emit light in the visible spectrum, and the color of the light emitted depends on its temperature. At lower temperatures, the metal appears dull red, and as the temperature increases, it progresses through shades of orange, yellow, and eventually to white or blue-white at extremely high temperatures.
For a stove burner, the red color is usually seen when the metal is at a high but not the highest temperature. The red-hot burner indicates that it's in the typical cooking temperature range and is ready for cooking food placed on it. The temperature can be controlled by adjusting the stove's settings or flame intensity.
It's important to exercise caution around red-hot stove burners to avoid burns and other injuries. Always use appropriate cookware and handle hot items with protective equipment or utensils.